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What are Systematic Reviews? (3 minutes, 24 second YouTube Video)

Systematic Literature Reviews: Steps & Resources

medical literature review example pdf

These steps for conducting a systematic literature review are listed below . 

Also see subpages for more information about:

  • The different types of literature reviews, including systematic reviews and other evidence synthesis methods
  • Tools & Tutorials

Literature Review & Systematic Review Steps

  • Develop a Focused Question
  • Scope the Literature  (Initial Search)
  • Refine & Expand the Search
  • Limit the Results
  • Download Citations
  • Abstract & Analyze
  • Create Flow Diagram
  • Synthesize & Report Results

1. Develop a Focused   Question 

Consider the PICO Format: Population/Problem, Intervention, Comparison, Outcome

Focus on defining the Population or Problem and Intervention (don't narrow by Comparison or Outcome just yet!)

"What are the effects of the Pilates method for patients with low back pain?"

Tools & Additional Resources:

  • PICO Question Help
  • Stillwell, Susan B., DNP, RN, CNE; Fineout-Overholt, Ellen, PhD, RN, FNAP, FAAN; Melnyk, Bernadette Mazurek, PhD, RN, CPNP/PMHNP, FNAP, FAAN; Williamson, Kathleen M., PhD, RN Evidence-Based Practice, Step by Step: Asking the Clinical Question, AJN The American Journal of Nursing : March 2010 - Volume 110 - Issue 3 - p 58-61 doi: 10.1097/01.NAJ.0000368959.11129.79

2. Scope the Literature

A "scoping search" investigates the breadth and/or depth of the initial question or may identify a gap in the literature. 

Eligible studies may be located by searching in:

  • Background sources (books, point-of-care tools)
  • Article databases
  • Trial registries
  • Grey literature
  • Cited references
  • Reference lists

When searching, if possible, translate terms to controlled vocabulary of the database. Use text word searching when necessary.

Use Boolean operators to connect search terms:

  • Combine separate concepts with AND  (resulting in a narrower search)
  • Connecting synonyms with OR  (resulting in an expanded search)

Search:  pilates AND ("low back pain"  OR  backache )

Video Tutorials - Translating PICO Questions into Search Queries

  • Translate Your PICO Into a Search in PubMed (YouTube, Carrie Price, 5:11) 
  • Translate Your PICO Into a Search in CINAHL (YouTube, Carrie Price, 4:56)

3. Refine & Expand Your Search

Expand your search strategy with synonymous search terms harvested from:

  • database thesauri
  • reference lists
  • relevant studies

Example: 

(pilates OR exercise movement techniques) AND ("low back pain" OR backache* OR sciatica OR lumbago OR spondylosis)

As you develop a final, reproducible strategy for each database, save your strategies in a:

  • a personal database account (e.g., MyNCBI for PubMed)
  • Log in with your NYU credentials
  • Open and "Make a Copy" to create your own tracker for your literature search strategies

4. Limit Your Results

Use database filters to limit your results based on your defined inclusion/exclusion criteria.  In addition to relying on the databases' categorical filters, you may also need to manually screen results.  

  • Limit to Article type, e.g.,:  "randomized controlled trial" OR multicenter study
  • Limit by publication years, age groups, language, etc.

NOTE: Many databases allow you to filter to "Full Text Only".  This filter is  not recommended . It excludes articles if their full text is not available in that particular database (CINAHL, PubMed, etc), but if the article is relevant, it is important that you are able to read its title and abstract, regardless of 'full text' status. The full text is likely to be accessible through another source (a different database, or Interlibrary Loan).  

  • Filters in PubMed
  • CINAHL Advanced Searching Tutorial

5. Download Citations

Selected citations and/or entire sets of search results can be downloaded from the database into a citation management tool. If you are conducting a systematic review that will require reporting according to PRISMA standards, a citation manager can help you keep track of the number of articles that came from each database, as well as the number of duplicate records.

In Zotero, you can create a Collection for the combined results set, and sub-collections for the results from each database you search.  You can then use Zotero's 'Duplicate Items" function to find and merge duplicate records.

File structure of a Zotero library, showing a combined pooled set, and sub folders representing results from individual databases.

  • Citation Managers - General Guide

6. Abstract and Analyze

  • Migrate citations to data collection/extraction tool
  • Screen Title/Abstracts for inclusion/exclusion
  • Screen and appraise full text for relevance, methods, 
  • Resolve disagreements by consensus

Covidence is a web-based tool that enables you to work with a team to screen titles/abstracts and full text for inclusion in your review, as well as extract data from the included studies.

Screenshot of the Covidence interface, showing Title and abstract screening phase.

  • Covidence Support
  • Critical Appraisal Tools
  • Data Extraction Tools

7. Create Flow Diagram

The PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) flow diagram is a visual representation of the flow of records through different phases of a systematic review.  It depicts the number of records identified, included and excluded.  It is best used in conjunction with the PRISMA checklist .

Example PRISMA diagram showing number of records identified, duplicates removed, and records excluded.

Example from: Stotz, S. A., McNealy, K., Begay, R. L., DeSanto, K., Manson, S. M., & Moore, K. R. (2021). Multi-level diabetes prevention and treatment interventions for Native people in the USA and Canada: A scoping review. Current Diabetes Reports, 2 (11), 46. https://doi.org/10.1007/s11892-021-01414-3

  • PRISMA Flow Diagram Generator (ShinyApp.io, Haddaway et al. )
  • PRISMA Diagram Templates  (Word and PDF)
  • Make a copy of the file to fill out the template
  • Image can be downloaded as PDF, PNG, JPG, or SVG
  • Covidence generates a PRISMA diagram that is automatically updated as records move through the review phases

8. Synthesize & Report Results

There are a number of reporting guideline available to guide the synthesis and reporting of results in systematic literature reviews.

It is common to organize findings in a matrix, also known as a Table of Evidence (ToE).

Example of a review matrix, using Microsoft Excel, showing the results of a systematic literature review.

  • Reporting Guidelines for Systematic Reviews
  • Download a sample template of a health sciences review matrix  (GoogleSheets)

Steps modified from: 

Cook, D. A., & West, C. P. (2012). Conducting systematic reviews in medical education: a stepwise approach.   Medical Education , 46 (10), 943–952.

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Performing a literature review

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  • 1 Institute of Biomedical Research, College of Medical and Dental Sciences, School of Immunity and Infection, University of Birmingham, UK

A necessary skill for any doctor

What causes disease, which drug is best, does this patient need surgery, and what is the prognosis? Although experience helps in answering these questions, ultimately they are best answered by evidence based medicine. But how do you assess the evidence? As a medical student, and throughout your career as a doctor, critical appraisal of published literature is an important skill to develop and refine. At medical school you will repeatedly appraise published literature and write literature reviews. These activities are commonly part of a special study module, research project for an intercalated degree, or another type of essay based assignment.

Formulating a question

Literature reviews are most commonly performed to help answer a particular question. While you are at medical school, there will usually be some choice regarding the area you are going to review.

Once you have identified a subject area for review, the next step is to formulate a specific research question. This is arguably the most important step because a clear question needs to be defined from the outset, which you aim to answer by doing the review. The clearer the question, the more likely it is that the answer will be clear too. It is important to have discussions with your supervisor when formulating a research question as his or her input will be invaluable. The research question must be objective and concise because it is easier to search through the evidence with a clear question. The question also needs to be feasible. What is the point in having a question for which no published evidence exists? Your supervisor’s input will ensure you are not trying to answer an unrealistic question. Finally, is the research question clinically important? There are many research questions that may be answered, but not all of them will be relevant to clinical practice. The research question we will use as an example to work through in this article is, “What is the evidence for using angiotensin converting enzyme (ACE) inhibitors in patients with hypertension?”

Collecting the evidence

After formulating a specific research question for your literature review, the next step is to collect the evidence. Your supervisor will initially point you in the right direction by highlighting some of the more relevant papers published. Before doing the literature search it is important to agree a list of keywords with your supervisor. A source of useful keywords can be obtained by reading Cochrane reviews or other systematic reviews, such as those published in the BMJ . 1 2 A relevant Cochrane review for our research question on ACE inhibitors in hypertension is that by Heran and colleagues. 3 Appropriate keywords to search for the evidence include the words used in your research question (“angiotensin converting enzyme inhibitor,” “hypertension,” “blood pressure”), details of the types of study you are looking for (“randomised controlled trial,” “case control,” “cohort”), and the specific drugs you are interested in (that is, the various ACE inhibitors such as “ramipril,” “perindopril,” and “lisinopril”).

Once keywords have been agreed it is time to search for the evidence using the various electronic medical databases (such as PubMed, Medline, and EMBASE). PubMed is the largest of these databases and contains online information and tutorials on how to do literature searches with worked examples. Searching the databases and obtaining the articles are usually free of charge through the subscription that your university pays. Early consultation with a medical librarian is important as it will help you perform your literature search in an impartial manner, and librarians can train you to do these searches for yourself.

Literature searches can be broad or tailored to be more specific. With our example, a broad search would entail searching all articles that contain the words “blood pressure” or “ACE inhibitor.” This provides a comprehensive list of all the literature, but there are likely to be thousands of articles to review subsequently (fig 1). ⇓ In contrast, various search restrictions can be applied on the electronic databases to filter out papers that may not be relevant to your review. Figure 2 gives an example of a specific search. ⇓ The search terms used in this case were “angiotensin converting enzyme inhibitor” and “hypertension.” The limits applied to this search were all randomised controlled trials carried out in humans, published in the English language over the last 10 years, with the search terms appearing in the title of the study only. Thus the more specific the search strategy, the more manageable the number of articles to review (fig 3), and this will save you time. ⇓ However, this method risks your not identifying all the evidence in the particular field. Striking a balance between a broad and a specific search strategy is therefore important. This will come with experience and consultation with your supervisor. It is important to note that evidence is continually becoming available on these electronic databases and therefore repeating the same search at a later date can provide new evidence relevant to your review.

Figure1

Fig 1 Results from a broad literature search using the term “angiotensin converting enzyme inhibitor”

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Figure2

Fig 2 Example of a specific literature search. The search terms used were “angiotensin converting enzyme inhibitor” and “hypertension.” The limits applied to this search were all randomised controlled trials carried out in humans, published in English over the past 10 years, with the search terms appearing in the title of the study only

Figure3

Fig 3 Results from a specific literature search (using the search terms and limits from figure 2)

Reading the abstracts (study summary) of the articles identified in your search may help you decide whether the study is applicable for your review—for example, the work may have been carried out using an animal model rather than in humans. After excluding any inappropriate articles, you need to obtain the full articles of studies you have identified. Additional relevant articles that may not have come up in your original search can also be found by searching the reference lists of the articles you have already obtained. Once again, you may find that some articles are still not applicable for your review, and these can also be excluded at this stage. It is important to explain in your final review what criteria you used to exclude articles as well as those criteria used for inclusion.

The National Institute for Health and Clinical Excellence (NICE) publishes evidence based guidelines for the United Kingdom and therefore provides an additional resource for identifying the relevant literature in a particular field. 4 NICE critically appraises the published literature with recommendations for best clinical practice proposed and graded based on the quality of evidence available. Similarly, there are internationally published evidence based guidelines, such as those produced by the European Society of Cardiology and the American College of Chest Physicians, which can be useful when collecting the literature in a particular field. 5 6

Appraising the evidence

Once you have collected the evidence, you need to critically appraise the published material. Box 1 gives definitions of terms you will encounter when reading the literature. A brief guide of how to critically appraise a study is presented; however, it is advisable to consult the references cited for further details.

Box 1: Definitions of common terms in the literature 7

Prospective—collecting data in real time after the study is designed

Retrospective—analysis of data that have already been collected to determine associations between exposure and outcome

Hypothesis—proposed association between exposure and outcome. If presented in the negative it is called the null hypothesis

Variable—a quantity or quality that changes during the study and can be measured

Single blind—subjects are unaware of their treatment, but clinicians are aware

Double blind—both subjects and clinicians are unaware of treatment given

Placebo—a simulated medical intervention, with subjects not receiving the specific intervention or treatment being studied

Outcome measure/endpoint—clinical variable or variables measured in a study subsequently used to make conclusions about the original interventions or treatments administered

Bias—difference between reported results and true results. Many types exist (such as selection, allocation, and reporting biases)

Probability (P) value—number between 0 and 1 providing the likelihood the reported results occurred by chance. A P value of 0.05 means there is a 5% likelihood that the reported result occurred by chance

Confidence intervals—provides a range between two numbers within which one can be certain the results lie. A confidence interval of 95% means one can be 95% certain the actual results lie within the reported range

The study authors should clearly define their research question and ideally the hypothesis to be tested. If the hypothesis is presented in the negative, it is called the null hypothesis. An example of a null hypothesis is smoking does not cause lung cancer. The study is then performed to assess the significance of the exposure (smoking) on outcome (lung cancer).

A major part of the critical appraisal process is to focus on study methodology, with your key task being an assessment of the extent to which a study was susceptible to bias (the discrepancy between the reported results and the true results). It should be clear from the methods what type of study was performed (box 2).

Box 2: Different study types 7

Systematic review/meta-analysis—comprehensive review of published literature using predefined methodology. Meta-analyses combine results from various studies to give numerical data for the overall association between variables

Randomised controlled trial—random allocation of patients to one of two or more groups. Used to test a new drug or procedure

Cohort study—two or more groups followed up over a long period, with one group exposed to a certain agent (drug or environmental agent) and the other not exposed, with various outcomes compared. An example would be following up a group of smokers and a group of non-smokers with the outcome measure being the development of lung cancer

Case-control study—cases (those with a particular outcome) are matched as closely as possible (for age, sex, ethnicity) with controls (those without the particular outcome). Retrospective data analysis is performed to determine any factors associated with developing the particular outcomes

Cross sectional study—looks at a specific group of patients at a single point in time. Effectively a survey. An example is asking a group of people how many of them drink alcohol

Case report—detailed reports concerning single patients. Useful in highlighting adverse drug reactions

There are many different types of bias, which depend on the particular type of study performed, and it is important to look for these biases. Several published checklists are available that provide excellent resources to help you work through the various studies and identify sources of bias. The CONSORT statement (which stands for CONsolidated Standards Of Reporting Trials) provides a minimum set of recommendations for reporting randomised controlled trials and comprises a rigorous 25 item checklist, with variations available for other study types. 8 9 As would be expected, most (17 of 25) of the items focus on questions relating to the methods and results of the randomised trial. The remaining items relate to the title, abstract, introduction, and discussion of the study, in addition to questions on trial registration, protocol, and funding.

Jadad scoring provides a simple and validated system to assess the methodological quality of a randomised clinical trial using three questions. 10 The score ranges from zero to five, with one point given for a “yes” in each of the following questions. (1) Was the study described as randomised? (2) Was the study described as double blind? (3) Were there details of subject withdrawals, exclusions, and dropouts? A further point is given if (1) the method of randomisation was appropriate, and (2) the method of blinding was appropriate.

In addition, the Critical Appraisal Skills Programme provides excellent tools for assessing the evidence in all study types (box 2). 11 The Oxford Centre for Evidence-Based Medicine levels of evidence is yet another useful resource for assessing the methodological quality of all studies. 12

Ensure all patients have been accounted for and any exclusions, for whatever reason, are reported. Knowing the baseline demographic (age, sex, ethnicity) and clinical characteristics of the population is important. Results are usually reported as probability values or confidence intervals (box 1).

This should explain the major study findings, put the results in the context of the published literature, and attempt to account for any variations from previous work. Study limitations and sources of bias should be discussed. Authors’ conclusions should be supported by the study results and not unnecessarily extrapolated. For example, a treatment shown to be effective in animals does not necessarily mean it will work in humans.

The format for writing up the literature review usually consists of an abstract (short structured summary of the review), the introduction or background, methods, results, and discussion with conclusions. There are a number of good examples of how to structure a literature review and these can be used as an outline when writing your review. 13 14

The introduction should identify the specific research question you intend to address and briefly put this into the context of the published literature. As you have now probably realised, the methods used for the review must be clear to the reader and provide the necessary detail for someone to be able to reproduce the search. The search strategy needs to include a list of keywords used, which databases were searched, and the specific search limits or filters applied. Any grading of methodological quality, such as the CONSORT statement or Jadad scoring, must be explained in addition to any study inclusion or exclusion criteria. 6 7 8 The methods also need to include a section on the data collected from each of the studies, the specific outcomes of interest, and any statistical analysis used. The latter point is usually relevant only when performing meta-analyses.

The results section must clearly show the process of filtering down from the articles obtained from the original search to the final studies included in the review—that is, accounting for all excluded studies. A flowchart is usually best to illustrate this. Next should follow a brief description of what was done in the main studies, the number of participants, the relevant results, and any potential sources of bias. It is useful to group similar studies together as it allows comparisons to be made by the reader and saves repetition in your write-up. Boxes and figures should be used appropriately to illustrate important findings from the various studies.

Finally, in the discussion you need to consider the study findings in light of the methodological quality—that is, the extent of potential bias in each study that may have affected the study results. Using the evidence, you need to make conclusions in your review, and highlight any important gaps in the evidence base, which need to be dealt with in future studies. Working through drafts of the literature review with your supervisor will help refine your critical appraisal skills and the ability to present information concisely in a structured review article. Remember, if the work is good it may get published.

Originally published as: Student BMJ 2012;20:e404

Competing interests: None declared.

Provenance and peer review: Not commissioned; externally peer reviewed.

  • ↵ The Cochrane Library. www3.interscience.wiley.com/cgibin/mrwhome/106568753/HOME?CRETRY=1&SRETRY=0 .
  • ↵ British Medical Journal . www.bmj.com/ .
  • ↵ Heran BS, Wong MMY, Heran IK, Wright JM. Blood pressure lowering efficacy of angiotensin converting enzyme (ACE) inhibitors for primary hypertension. Cochrane Database Syst Rev 2008 ; 4 : CD003823 , doi: 10.1002/14651858.CD003823.pub2. OpenUrl PubMed
  • ↵ National Institute for Health and Clinical Excellence. www.nice.org.uk .
  • ↵ European Society of Cardiology. www.escardio.org/guidelines .
  • ↵ Geerts WH, Bergqvist D, Pineo GF, Heit JA, Samama CM, Lassen MR, et al. Prevention of venous thromboembolism: American College of Chest Physicians evidence-based clinical practice guidelines (8th ed). Chest 2008 ; 133 : 381 -453S. OpenUrl CrossRef
  • ↵ Wikipedia. http://en.wikipedia.org/wiki .
  • ↵ Moher D, Schulz KF, Altman DG, Egger M, Davidoff F, Elbourne D, et al. The CONSORT statement: revised recommendations for improving the quality of reports of parallel-group randomised trials. Lancet 2001 ; 357 : 1191 -4. OpenUrl CrossRef PubMed Web of Science
  • ↵ The CONSORT statement. www.consort-statement.org/ .
  • ↵ Jadad AR, Moore RA, Carroll D, Jenkinson C, Reynolds DJ, Gavaghan DJ, et al. Assessing the quality of reports of randomized clinical trials: is blinding necessary? Control Clin Trials 1996 ; 17 : 1 -12. OpenUrl CrossRef PubMed Web of Science
  • ↵ Critical Appraisal Skills Programme (CASP). www.sph.nhs.uk/what-we-do/public-health-workforce/resources/critical-appraisals-skills-programme .
  • ↵ Oxford Centre for Evidence-based Medicine—Levels of Evidence. www.cebm.net .
  • ↵ Van den Bruel A, Thompson MJ, Haj-Hassan T, Stevens R, Moll H, Lakhanpaul M, et al . Diagnostic value of laboratory tests in identifying serious infections in febrile children: systematic review. BMJ 2011 ; 342 : d3082 . OpenUrl Abstract / FREE Full Text
  • ↵ Awopetu AI, Moxey P, Hinchliffe RJ, Jones KG, Thompson MM, Holt PJ. Systematic review and meta-analysis of the relationship between hospital volume and outcome for lower limb arterial surgery. Br J Surg 2010 ; 97 : 797 -803. OpenUrl CrossRef PubMed

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  • Meeting the review family: exploring review types and associated information retrieval requirements | Health Information and Libraries Journal, 2019
  • A typology of reviews: an analysis of 14 review types and associated methodologies | Health Information and Libraries Journal, 2009
  • Conceptual recommendations for selecting the most appropriate knowledge synthesis method to answer research questions related to complex evidence | Journal of Clinical Epidemiology, 2016
  • Methods for knowledge synthesis: an overview | Heart & Lung: The Journal of Critical Care, 2014
  • Not sure what type of review to conduct? Brief descriptions of each type plus tools to help you decide

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  • The Purpose, Process, and Methods of Writing a Literature Review | AORN Journal. 2016
  • Why, When, Who, What, How, and Where for Trainees Writing Literature Review Articles. | Annals of Biomed Engineering, 2019
  • So You Want to Write a Narrative Review Article? | Journal of Cardiothoracic and Anesthesia, 2021
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  • The Literature Review: A Foundation for High-Quality Medical Education Research | Journal of Graduate Medical Education, 2016
  • Writing an effective literature review : Part I: Mapping the gap | Perspectives on Medical Education, 2018
  • Writing an effective literature review : Part II: Citation technique | Perspectives on Medical Education, 2018
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JAY SIWEK, M.D., MARGARET L. GOURLAY, M.D., DAVID C. SLAWSON, M.D., AND ALLEN F. SHAUGHNESSY, PHARM.D.

Am Fam Physician. 2002;65(2):251-258

Traditional clinical review articles, also known as updates, differ from systematic reviews and meta-analyses. Updates selectively review the medical literature while discussing a topic broadly. Nonquantitative systematic reviews comprehensively examine the medical literature, seeking to identify and synthesize all relevant information to formulate the best approach to diagnosis or treatment. Meta-analyses (quantitative systematic reviews) seek to answer a focused clinical question, using rigorous statistical analysis of pooled research studies. This article presents guidelines for writing an evidence-based clinical review article for American Family Physician . First, the topic should be of common interest and relevance to family practice. Include a table of the continuing medical education objectives of the review. State how the literature search was done and include several sources of evidence-based reviews, such as the Cochrane Collaboration, BMJ's Clinical Evidence , or the InfoRetriever Web site. Where possible, use evidence based on clinical outcomes relating to morbidity, mortality, or quality of life, and studies of primary care populations. In articles submitted to American Family Physician , rate the level of evidence for key recommendations according to the following scale: level A (randomized controlled trial [RCT], meta-analysis); level B (other evidence); level C (consensus/expert opinion). Finally, provide a table of key summary points.

American Family Physician is particularly interested in receiving clinical review articles that follow an evidence-based format. Clinical review articles, also known as updates, differ from systematic reviews and meta-analyses in important ways. 1 Updates selectively review the medical literature while discussing a topic broadly. An example of such a topic is, “The diagnosis and treatment of myocardial ischemia.” Systematic reviews comprehensively examine the medical literature, seeking to identify and synthesize all relevant information to formulate the best approach to diagnosis or treatment. Examples are many of the systematic reviews of the Cochrane Collaboration or BMJ's Clinical Evidence compendium. Meta-analyses are a special type of systematic review. They use quantitative methods to analyze the literature and seek to answer a focused clinical question, using rigorous statistical analysis of pooled research studies. An example is, “Do beta blockers reduce mortality following myocardial infarction?”

The best clinical review articles base the discussion on existing systematic reviews and meta-analyses, and incorporate all relevant research findings about the management of a given disorder. Such evidence-based updates provide readers with powerful summaries and sound clinical guidance.

In this article, we present guidelines for writing an evidence-based clinical review article, especially one designed for continuing medical education (CME) and incorporating CME objectives into its format. This article may be read as a companion piece to a previous article and accompanying editorial about reading and evaluating clinical review articles. 1 , 2 Some articles may not be appropriate for an evidence-based format because of the nature of the topic, the slant of the article, a lack of sufficient supporting evidence, or other factors. We encourage authors to review the literature and, wherever possible, rate key points of evidence. This process will help emphasize the summary points of the article and strengthen its teaching value.

Topic Selection

Choose a common clinical problem and avoid topics that are rarities or unusual manifestations of disease or that have curiosity value only. Whenever possible, choose common problems for which there is new information about diagnosis or treatment. Emphasize new information that, if valid, should prompt a change in clinical practice, such as the recent evidence that spironolactone therapy improves survival in patients who have severe congestive heart failure. 3 Similarly, new evidence showing that a standard treatment is no longer helpful, but may be harmful, would also be important to report. For example, patching most traumatic corneal abrasions may actually cause more symptoms and delay healing compared with no patching. 4

Searching the Literature

When searching the literature on your topic, please consult several sources of evidence-based reviews ( Table 1 ) . Look for pertinent guidelines on the diagnosis, treatment, or prevention of the disorder being discussed. Incorporate all high-quality recommendations that are relevant to the topic. When reviewing the first draft, look for all key recommendations about diagnosis and, especially, treatment. Try to ensure that all recommendations are based on the highest level of evidence available. If you are not sure about the source or strength of the recommendation, return to the literature, seeking out the basis for the recommendation.

In particular, try to find the answer in an authoritative compendium of evidence-based reviews, or at least try to find a meta-analysis or well-designed randomized controlled trial (RCT) to support it. If none appears to be available, try to cite an authoritative consensus statement or clinical guideline, such as a National Institutes of Health Consensus Development Conference statement or a clinical guideline published by a major medical organization. If no strong evidence exists to support the conventional approach to managing a given clinical situation, point this out in the text, especially for key recommendations. Keep in mind that much of traditional medical practice has not yet undergone rigorous scientific study, and high-quality evidence may not exist to support conventional knowledge or practice.

Patient-Oriented vs. Disease-Oriented Evidence

With regard to types of evidence, Shaughnessy and Slawson 5 – 7 developed the concept of Patient-Oriented Evidence that Matters (POEM), in distinction to Disease-Oriented Evidence (DOE). POEM deals with outcomes of importance to patients, such as changes in morbidity, mortality, or quality of life. DOE deals with surrogate end points, such as changes in laboratory values or other measures of response. Although the results of DOE sometimes parallel the results of POEM, they do not always correspond ( Table 2 ) . 2 When possible, use POEM-type evidence rather than DOE. When DOE is the only guidance available, indicate that key clinical recommendations lack the support of outcomes evidence. Here is an example of how the latter situation might appear in the text: “Although prostate-specific antigen (PSA) testing identifies prostate cancer at an early stage, it has not yet been proved that PSA screening improves patient survival.” (Note: PSA testing is an example of DOE, a surrogate marker for the true outcomes of importance—improved survival, decreased morbidity, and improved quality of life.)

Evaluating the Literature

Evaluate the strength and validity of the literature that supports the discussion (see the following section, Levels of Evidence). Look for meta-analyses, high-quality, randomized clinical trials with important outcomes (POEM), or well-designed, nonrandomized clinical trials, clinical cohort studies, or case-controlled studies with consistent findings. In some cases, high-quality, historical, uncontrolled studies are appropriate (e.g., the evidence supporting the efficacy of Papanicolaou smear screening). Avoid anecdotal reports or repeating the hearsay of conventional wisdom, which may not stand up to the scrutiny of scientific study (e.g., prescribing prolonged bed rest for low back pain).

Look for studies that describe patient populations that are likely to be seen in primary care rather than subspecialty referral populations. Shaughnessy and Slawson's guide for writers of clinical review articles includes a section on information and validity traps to avoid. 2

Levels of Evidence

Readers need to know the strength of the evidence supporting the key clinical recommendations on diagnosis and treatment. Many different rating systems of varying complexity and clinical relevance are described in the medical literature. Recently, the third U.S. Preventive Services Task Force (USPSTF) emphasized the importance of rating not only the study type (RCT, cohort study, case-control study, etc.), but also the study quality as measured by internal validity and the quality of the entire body of evidence on a topic. 8

While it is important to appreciate these evolving concepts, we find that a simplified grading system is more useful in AFP . We have adopted the following convention, using an ABC rating scale. Criteria for high-quality studies are discussed in several sources. 8 , 9 See the AFP Web site ( www.aafp.org/afp/authors ) for additional information about levels of evidence and see the accompanying editorial in this issue discussing the potential pitfalls and limitations of any rating system.

Level A (randomized controlled trial/meta-analysis): High-quality randomized controlled trial (RCT) that considers all important outcomes. High-quality meta-analysis (quantitative systematic review) using comprehensive search strategies.

Level B (other evidence): A well-designed, nonrandomized clinical trial. A nonquantitative systematic review with appropriate search strategies and well-substantiated conclusions. Includes lower quality RCTs, clinical cohort studies, and case-controlled studies with non-biased selection of study participants and consistent findings. Other evidence, such as high-quality, historical, uncontrolled studies, or well-designed epidemiologic studies with compelling findings, is also included.

Level C (consensus/expert opinion): Consensus viewpoint or expert opinion.

Each rating is applied to a single reference in the article, not to the entire body of evidence that exists on a topic. Each label should include the letter rating (A, B, C), followed by the specific type of study for that reference. For example, following a level B rating, include one of these descriptors: (1) nonrandomized clinical trial; (2) nonquantitative systematic review; (3) lower quality RCT; (4) clinical cohort study; (5) case-controlled study; (6) historical uncontrolled study; (7) epidemiologic study.

Here are some examples of the way evidence ratings should appear in the text:

“To improve morbidity and mortality, most patients in congestive heart failure should be treated with an angiotensin-converting enzyme inhibitor. [Evidence level A, RCT]”

“The USPSTF recommends that clinicians routinely screen asymptomatic pregnant women 25 years and younger for chlamydial infection. [Evidence level B, non-randomized clinical trial]”

“The American Diabetes Association recommends screening for diabetes every three years in all patients at high risk of the disease, including all adults 45 years and older. [Evidence level C, expert opinion]”

When scientifically strong evidence does not exist to support a given clinical recommendation, you can point this out in the following way:

“Physical therapy is traditionally prescribed for the treatment of adhesive capsulitis (frozen shoulder), although there are no randomized outcomes studies of this approach.”

Format of the Review

Introduction.

The introduction should define the topic and purpose of the review and describe its relevance to family practice. The traditional way of doing this is to discuss the epidemiology of the condition, stating how many people have it at one point in time (prevalence) or what percentage of the population is expected to develop it over a given period of time (incidence). A more engaging way of doing this is to indicate how often a typical family physician is likely to encounter this problem during a week, month, year, or career. Emphasize the key CME objectives of the review and summarize them in a separate table entitled “CME Objectives.”

The methods section should briefly indicate how the literature search was conducted and what major sources of evidence were used. Ideally, indicate what predetermined criteria were used to include or exclude studies (e.g., studies had to be independently rated as being high quality by an established evaluation process, such as the Cochrane Collaboration). Be comprehensive in trying to identify all major relevant research. Critically evaluate the quality of research reviewed. Avoid selective referencing of only information that supports your conclusions. If there is controversy on a topic, address the full scope of the controversy.

The discussion can then follow the typical format of a clinical review article. It should touch on one or more of the following subtopics: etiology, pathophysiology, clinical presentation (signs and symptoms), diagnostic evaluation (history, physical examination, laboratory evaluation, and diagnostic imaging), differential diagnosis, treatment (goals, medical/surgical therapy, laboratory testing, patient education, and follow-up), prognosis, prevention, and future directions.

The review will be comprehensive and balanced if it acknowledges controversies, unresolved questions, recent developments, other viewpoints, and any apparent conflicts of interest or instances of bias that might affect the strength of the evidence presented. Emphasize an evidence-supported approach or, where little evidence exists, a consensus viewpoint. In the absence of a consensus viewpoint, you may describe generally accepted practices or discuss one or more reasoned approaches, but acknowledge that solid support for these recommendations is lacking.

In some cases, cost-effectiveness analyses may be important in deciding how to implement health care services, especially preventive services. 10 When relevant, mention high-quality cost-effectiveness analyses to help clarify the costs and health benefits associated with alternative interventions to achieve a given health outcome. Highlight key points about diagnosis and treatment in the discussion and include a summary table of the key take-home points. These points are not necessarily the same as the key recommendations, whose level of evidence is rated, although some of them will be.

Use tables, figures, and illustrations to highlight key points, and present a step-wise, algorithmic approach to diagnosis or treatment when possible.

Rate the evidence for key statements, especially treatment recommendations. We expect that most articles will have at most two to four key statements; some will have none. Rate only those statements that have corresponding references and base the rating on the quality and level of evidence presented in the supporting citations. Use primary sources (original research, RCTs, meta-analyses, and systematic reviews) as the basis for determining the level of evidence. In other words, the supporting citation should be a primary research source of the information, not a secondary source (such as a nonsystematic review article or a textbook) that simply cites the original source. Systematic reviews that analyze multiple RCTs are good sources for determining ratings of evidence.

The references should include the most current and important sources of support for key statements (i.e., studies referred to, new information, controversial material, specific quantitative data, and information that would not usually be found in most general reference textbooks). Generally, these references will be key evidence-based recommendations, meta-analyses, or landmark articles. Although some journals publish exhaustive lists of reference citations, AFP prefers to include a succinct list of key references. (We will make more extensive reference lists available on our Web site or provide links to your personal reference list.)

You may use the following checklist to ensure the completeness of your evidence-based review article; use the source list of reviews to identify important sources of evidence-based medicine materials.

Checklist for an Evidence-Based Clinical Review Article

The topic is common in family practice, especially topics in which there is new, important information about diagnosis or treatment.

The introduction defines the topic and the purpose of the review, and describes its relevance to family practice.

A table of CME objectives for the review is included.

The review states how you did your literature search and indicates what sources you checked to ensure a comprehensive assessment of relevant studies (e.g., MEDLINE, the Cochrane Collaboration Database, the Center for Research Support, TRIP Database).

Several sources of evidence-based reviews on the topic are evaluated ( Table 1 ) .

Where possible, POEM (dealing with changes in morbidity, mortality, or quality of life) rather than DOE (dealing with mechanistic explanations or surrogate end points, such as changes in laboratory tests) is used to support key clinical recommendations ( Table 2 ) .

Studies of patients likely to be representative of those in primary care practices, rather than subspecialty referral centers, are emphasized.

Studies that are not only statistically significant but also clinically significant are emphasized; e.g., interventions with meaningful changes in absolute risk reduction and low numbers needed to treat. (See http://www.cebm.net/index.aspx?o=1116 .) 11

The level of evidence for key clinical recommendations is labeled using the following rating scale: level A (RCT/meta-analysis), level B (other evidence), and level C (consensus/expert opinion).

Acknowledge controversies, recent developments, other viewpoints, and any apparent conflicts of interest or instances of bias that might affect the strength of the evidence presented.

Highlight key points about diagnosis and treatment in the discussion and include a summary table of key take-home points.

Use tables, figures, and illustrations to highlight key points and present a step-wise, algorithmic approach to diagnosis or treatment when possible.

Emphasize evidence-based guidelines and primary research studies, rather than other review articles, unless they are systematic reviews.

The essential elements of this checklist are summarized in Table 3 .

Siwek J. Reading and evaluating clinical review articles. Am Fam Physician. 1997;55:2064-2069.

Shaughnessy AF, Slawson DC. Getting the most from review articles: a guide for readers and writers. Am Fam Physician. 1997;55:2155-60.

Pitt B, Zannad F, Remme WJ, Cody R, Castaigne A, Perez A, et al. The effect of spironolactone on morbidity and mortality in patients with severe heart failure. N Engl J Med. 1999;341:709-17.

Flynn CA, D'Amico F, Smith G. Should we patch corneal abrasions? A meta-analysis. J Fam Pract. 1998;47:264-70.

Slawson DC, Shaughnessy AF, Bennett JH. Becoming a medical information master: feeling good about not knowing everything. J Fam Pract. 1994;38:505-13.

Shaughnessy AF, Slawson DC, Bennett JH. Becoming an information master: a guidebook to the medical information jungle. J Fam Pract. 1994;39:489-99.

Slawson DC, Shaughnessy AF. Becoming an information master: using POEMs to change practice with confidence. Patient-oriented evidence that matters. J Fam Pract. 2000;49:63-7.

Harris RP, Helfand M, Woolf SH, Lohr KN, Mulrow CD, Teutsch SM, et al. Methods Work Group, Third U.S. Preventive Services Task Force. Current methods of the U.S. Preventive Services Task Force. A review of the process. Am J Prev Med. 2001;20(3 suppl):21-35.

CATbank topics: levels of evidence and grades of recommendations. Retrieved November 2001, from: http://www.cebm.net/ .

Saha S, Hoerger TJ, Pignone MP, Teutsch SM, Helfand M, Mandelblatt JS. for the Cost Work Group of the Third U.S. Preventive Services Task Force. The art and science of incorporating cost effectiveness into evidence-based recommendations for clinical preventive services. Am J Prev Med. 2001;20(3 suppl):36-43.

Evidence-based medicine glossary. Retrieved November 2001, from: http://www.cebm.net/index.aspx?o=1116 .

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Lau F, Kuziemsky C, editors. Handbook of eHealth Evaluation: An Evidence-based Approach [Internet]. Victoria (BC): University of Victoria; 2017 Feb 27.

Cover of Handbook of eHealth Evaluation: An Evidence-based Approach

Handbook of eHealth Evaluation: An Evidence-based Approach [Internet].

Chapter 9 methods for literature reviews.

Guy Paré and Spyros Kitsiou .

9.1. Introduction

Literature reviews play a critical role in scholarship because science remains, first and foremost, a cumulative endeavour ( vom Brocke et al., 2009 ). As in any academic discipline, rigorous knowledge syntheses are becoming indispensable in keeping up with an exponentially growing eHealth literature, assisting practitioners, academics, and graduate students in finding, evaluating, and synthesizing the contents of many empirical and conceptual papers. Among other methods, literature reviews are essential for: (a) identifying what has been written on a subject or topic; (b) determining the extent to which a specific research area reveals any interpretable trends or patterns; (c) aggregating empirical findings related to a narrow research question to support evidence-based practice; (d) generating new frameworks and theories; and (e) identifying topics or questions requiring more investigation ( Paré, Trudel, Jaana, & Kitsiou, 2015 ).

Literature reviews can take two major forms. The most prevalent one is the “literature review” or “background” section within a journal paper or a chapter in a graduate thesis. This section synthesizes the extant literature and usually identifies the gaps in knowledge that the empirical study addresses ( Sylvester, Tate, & Johnstone, 2013 ). It may also provide a theoretical foundation for the proposed study, substantiate the presence of the research problem, justify the research as one that contributes something new to the cumulated knowledge, or validate the methods and approaches for the proposed study ( Hart, 1998 ; Levy & Ellis, 2006 ).

The second form of literature review, which is the focus of this chapter, constitutes an original and valuable work of research in and of itself ( Paré et al., 2015 ). Rather than providing a base for a researcher’s own work, it creates a solid starting point for all members of the community interested in a particular area or topic ( Mulrow, 1987 ). The so-called “review article” is a journal-length paper which has an overarching purpose to synthesize the literature in a field, without collecting or analyzing any primary data ( Green, Johnson, & Adams, 2006 ).

When appropriately conducted, review articles represent powerful information sources for practitioners looking for state-of-the art evidence to guide their decision-making and work practices ( Paré et al., 2015 ). Further, high-quality reviews become frequently cited pieces of work which researchers seek out as a first clear outline of the literature when undertaking empirical studies ( Cooper, 1988 ; Rowe, 2014 ). Scholars who track and gauge the impact of articles have found that review papers are cited and downloaded more often than any other type of published article ( Cronin, Ryan, & Coughlan, 2008 ; Montori, Wilczynski, Morgan, Haynes, & Hedges, 2003 ; Patsopoulos, Analatos, & Ioannidis, 2005 ). The reason for their popularity may be the fact that reading the review enables one to have an overview, if not a detailed knowledge of the area in question, as well as references to the most useful primary sources ( Cronin et al., 2008 ). Although they are not easy to conduct, the commitment to complete a review article provides a tremendous service to one’s academic community ( Paré et al., 2015 ; Petticrew & Roberts, 2006 ). Most, if not all, peer-reviewed journals in the fields of medical informatics publish review articles of some type.

The main objectives of this chapter are fourfold: (a) to provide an overview of the major steps and activities involved in conducting a stand-alone literature review; (b) to describe and contrast the different types of review articles that can contribute to the eHealth knowledge base; (c) to illustrate each review type with one or two examples from the eHealth literature; and (d) to provide a series of recommendations for prospective authors of review articles in this domain.

9.2. Overview of the Literature Review Process and Steps

As explained in Templier and Paré (2015) , there are six generic steps involved in conducting a review article:

  • formulating the research question(s) and objective(s),
  • searching the extant literature,
  • screening for inclusion,
  • assessing the quality of primary studies,
  • extracting data, and
  • analyzing data.

Although these steps are presented here in sequential order, one must keep in mind that the review process can be iterative and that many activities can be initiated during the planning stage and later refined during subsequent phases ( Finfgeld-Connett & Johnson, 2013 ; Kitchenham & Charters, 2007 ).

Formulating the research question(s) and objective(s): As a first step, members of the review team must appropriately justify the need for the review itself ( Petticrew & Roberts, 2006 ), identify the review’s main objective(s) ( Okoli & Schabram, 2010 ), and define the concepts or variables at the heart of their synthesis ( Cooper & Hedges, 2009 ; Webster & Watson, 2002 ). Importantly, they also need to articulate the research question(s) they propose to investigate ( Kitchenham & Charters, 2007 ). In this regard, we concur with Jesson, Matheson, and Lacey (2011) that clearly articulated research questions are key ingredients that guide the entire review methodology; they underscore the type of information that is needed, inform the search for and selection of relevant literature, and guide or orient the subsequent analysis. Searching the extant literature: The next step consists of searching the literature and making decisions about the suitability of material to be considered in the review ( Cooper, 1988 ). There exist three main coverage strategies. First, exhaustive coverage means an effort is made to be as comprehensive as possible in order to ensure that all relevant studies, published and unpublished, are included in the review and, thus, conclusions are based on this all-inclusive knowledge base. The second type of coverage consists of presenting materials that are representative of most other works in a given field or area. Often authors who adopt this strategy will search for relevant articles in a small number of top-tier journals in a field ( Paré et al., 2015 ). In the third strategy, the review team concentrates on prior works that have been central or pivotal to a particular topic. This may include empirical studies or conceptual papers that initiated a line of investigation, changed how problems or questions were framed, introduced new methods or concepts, or engendered important debate ( Cooper, 1988 ). Screening for inclusion: The following step consists of evaluating the applicability of the material identified in the preceding step ( Levy & Ellis, 2006 ; vom Brocke et al., 2009 ). Once a group of potential studies has been identified, members of the review team must screen them to determine their relevance ( Petticrew & Roberts, 2006 ). A set of predetermined rules provides a basis for including or excluding certain studies. This exercise requires a significant investment on the part of researchers, who must ensure enhanced objectivity and avoid biases or mistakes. As discussed later in this chapter, for certain types of reviews there must be at least two independent reviewers involved in the screening process and a procedure to resolve disagreements must also be in place ( Liberati et al., 2009 ; Shea et al., 2009 ). Assessing the quality of primary studies: In addition to screening material for inclusion, members of the review team may need to assess the scientific quality of the selected studies, that is, appraise the rigour of the research design and methods. Such formal assessment, which is usually conducted independently by at least two coders, helps members of the review team refine which studies to include in the final sample, determine whether or not the differences in quality may affect their conclusions, or guide how they analyze the data and interpret the findings ( Petticrew & Roberts, 2006 ). Ascribing quality scores to each primary study or considering through domain-based evaluations which study components have or have not been designed and executed appropriately makes it possible to reflect on the extent to which the selected study addresses possible biases and maximizes validity ( Shea et al., 2009 ). Extracting data: The following step involves gathering or extracting applicable information from each primary study included in the sample and deciding what is relevant to the problem of interest ( Cooper & Hedges, 2009 ). Indeed, the type of data that should be recorded mainly depends on the initial research questions ( Okoli & Schabram, 2010 ). However, important information may also be gathered about how, when, where and by whom the primary study was conducted, the research design and methods, or qualitative/quantitative results ( Cooper & Hedges, 2009 ). Analyzing and synthesizing data : As a final step, members of the review team must collate, summarize, aggregate, organize, and compare the evidence extracted from the included studies. The extracted data must be presented in a meaningful way that suggests a new contribution to the extant literature ( Jesson et al., 2011 ). Webster and Watson (2002) warn researchers that literature reviews should be much more than lists of papers and should provide a coherent lens to make sense of extant knowledge on a given topic. There exist several methods and techniques for synthesizing quantitative (e.g., frequency analysis, meta-analysis) and qualitative (e.g., grounded theory, narrative analysis, meta-ethnography) evidence ( Dixon-Woods, Agarwal, Jones, Young, & Sutton, 2005 ; Thomas & Harden, 2008 ).

9.3. Types of Review Articles and Brief Illustrations

EHealth researchers have at their disposal a number of approaches and methods for making sense out of existing literature, all with the purpose of casting current research findings into historical contexts or explaining contradictions that might exist among a set of primary research studies conducted on a particular topic. Our classification scheme is largely inspired from Paré and colleagues’ (2015) typology. Below we present and illustrate those review types that we feel are central to the growth and development of the eHealth domain.

9.3.1. Narrative Reviews

The narrative review is the “traditional” way of reviewing the extant literature and is skewed towards a qualitative interpretation of prior knowledge ( Sylvester et al., 2013 ). Put simply, a narrative review attempts to summarize or synthesize what has been written on a particular topic but does not seek generalization or cumulative knowledge from what is reviewed ( Davies, 2000 ; Green et al., 2006 ). Instead, the review team often undertakes the task of accumulating and synthesizing the literature to demonstrate the value of a particular point of view ( Baumeister & Leary, 1997 ). As such, reviewers may selectively ignore or limit the attention paid to certain studies in order to make a point. In this rather unsystematic approach, the selection of information from primary articles is subjective, lacks explicit criteria for inclusion and can lead to biased interpretations or inferences ( Green et al., 2006 ). There are several narrative reviews in the particular eHealth domain, as in all fields, which follow such an unstructured approach ( Silva et al., 2015 ; Paul et al., 2015 ).

Despite these criticisms, this type of review can be very useful in gathering together a volume of literature in a specific subject area and synthesizing it. As mentioned above, its primary purpose is to provide the reader with a comprehensive background for understanding current knowledge and highlighting the significance of new research ( Cronin et al., 2008 ). Faculty like to use narrative reviews in the classroom because they are often more up to date than textbooks, provide a single source for students to reference, and expose students to peer-reviewed literature ( Green et al., 2006 ). For researchers, narrative reviews can inspire research ideas by identifying gaps or inconsistencies in a body of knowledge, thus helping researchers to determine research questions or formulate hypotheses. Importantly, narrative reviews can also be used as educational articles to bring practitioners up to date with certain topics of issues ( Green et al., 2006 ).

Recently, there have been several efforts to introduce more rigour in narrative reviews that will elucidate common pitfalls and bring changes into their publication standards. Information systems researchers, among others, have contributed to advancing knowledge on how to structure a “traditional” review. For instance, Levy and Ellis (2006) proposed a generic framework for conducting such reviews. Their model follows the systematic data processing approach comprised of three steps, namely: (a) literature search and screening; (b) data extraction and analysis; and (c) writing the literature review. They provide detailed and very helpful instructions on how to conduct each step of the review process. As another methodological contribution, vom Brocke et al. (2009) offered a series of guidelines for conducting literature reviews, with a particular focus on how to search and extract the relevant body of knowledge. Last, Bandara, Miskon, and Fielt (2011) proposed a structured, predefined and tool-supported method to identify primary studies within a feasible scope, extract relevant content from identified articles, synthesize and analyze the findings, and effectively write and present the results of the literature review. We highly recommend that prospective authors of narrative reviews consult these useful sources before embarking on their work.

Darlow and Wen (2015) provide a good example of a highly structured narrative review in the eHealth field. These authors synthesized published articles that describe the development process of mobile health ( m-health ) interventions for patients’ cancer care self-management. As in most narrative reviews, the scope of the research questions being investigated is broad: (a) how development of these systems are carried out; (b) which methods are used to investigate these systems; and (c) what conclusions can be drawn as a result of the development of these systems. To provide clear answers to these questions, a literature search was conducted on six electronic databases and Google Scholar . The search was performed using several terms and free text words, combining them in an appropriate manner. Four inclusion and three exclusion criteria were utilized during the screening process. Both authors independently reviewed each of the identified articles to determine eligibility and extract study information. A flow diagram shows the number of studies identified, screened, and included or excluded at each stage of study selection. In terms of contributions, this review provides a series of practical recommendations for m-health intervention development.

9.3.2. Descriptive or Mapping Reviews

The primary goal of a descriptive review is to determine the extent to which a body of knowledge in a particular research topic reveals any interpretable pattern or trend with respect to pre-existing propositions, theories, methodologies or findings ( King & He, 2005 ; Paré et al., 2015 ). In contrast with narrative reviews, descriptive reviews follow a systematic and transparent procedure, including searching, screening and classifying studies ( Petersen, Vakkalanka, & Kuzniarz, 2015 ). Indeed, structured search methods are used to form a representative sample of a larger group of published works ( Paré et al., 2015 ). Further, authors of descriptive reviews extract from each study certain characteristics of interest, such as publication year, research methods, data collection techniques, and direction or strength of research outcomes (e.g., positive, negative, or non-significant) in the form of frequency analysis to produce quantitative results ( Sylvester et al., 2013 ). In essence, each study included in a descriptive review is treated as the unit of analysis and the published literature as a whole provides a database from which the authors attempt to identify any interpretable trends or draw overall conclusions about the merits of existing conceptualizations, propositions, methods or findings ( Paré et al., 2015 ). In doing so, a descriptive review may claim that its findings represent the state of the art in a particular domain ( King & He, 2005 ).

In the fields of health sciences and medical informatics, reviews that focus on examining the range, nature and evolution of a topic area are described by Anderson, Allen, Peckham, and Goodwin (2008) as mapping reviews . Like descriptive reviews, the research questions are generic and usually relate to publication patterns and trends. There is no preconceived plan to systematically review all of the literature although this can be done. Instead, researchers often present studies that are representative of most works published in a particular area and they consider a specific time frame to be mapped.

An example of this approach in the eHealth domain is offered by DeShazo, Lavallie, and Wolf (2009). The purpose of this descriptive or mapping review was to characterize publication trends in the medical informatics literature over a 20-year period (1987 to 2006). To achieve this ambitious objective, the authors performed a bibliometric analysis of medical informatics citations indexed in medline using publication trends, journal frequencies, impact factors, Medical Subject Headings (MeSH) term frequencies, and characteristics of citations. Findings revealed that there were over 77,000 medical informatics articles published during the covered period in numerous journals and that the average annual growth rate was 12%. The MeSH term analysis also suggested a strong interdisciplinary trend. Finally, average impact scores increased over time with two notable growth periods. Overall, patterns in research outputs that seem to characterize the historic trends and current components of the field of medical informatics suggest it may be a maturing discipline (DeShazo et al., 2009).

9.3.3. Scoping Reviews

Scoping reviews attempt to provide an initial indication of the potential size and nature of the extant literature on an emergent topic (Arksey & O’Malley, 2005; Daudt, van Mossel, & Scott, 2013 ; Levac, Colquhoun, & O’Brien, 2010). A scoping review may be conducted to examine the extent, range and nature of research activities in a particular area, determine the value of undertaking a full systematic review (discussed next), or identify research gaps in the extant literature ( Paré et al., 2015 ). In line with their main objective, scoping reviews usually conclude with the presentation of a detailed research agenda for future works along with potential implications for both practice and research.

Unlike narrative and descriptive reviews, the whole point of scoping the field is to be as comprehensive as possible, including grey literature (Arksey & O’Malley, 2005). Inclusion and exclusion criteria must be established to help researchers eliminate studies that are not aligned with the research questions. It is also recommended that at least two independent coders review abstracts yielded from the search strategy and then the full articles for study selection ( Daudt et al., 2013 ). The synthesized evidence from content or thematic analysis is relatively easy to present in tabular form (Arksey & O’Malley, 2005; Thomas & Harden, 2008 ).

One of the most highly cited scoping reviews in the eHealth domain was published by Archer, Fevrier-Thomas, Lokker, McKibbon, and Straus (2011) . These authors reviewed the existing literature on personal health record ( phr ) systems including design, functionality, implementation, applications, outcomes, and benefits. Seven databases were searched from 1985 to March 2010. Several search terms relating to phr s were used during this process. Two authors independently screened titles and abstracts to determine inclusion status. A second screen of full-text articles, again by two independent members of the research team, ensured that the studies described phr s. All in all, 130 articles met the criteria and their data were extracted manually into a database. The authors concluded that although there is a large amount of survey, observational, cohort/panel, and anecdotal evidence of phr benefits and satisfaction for patients, more research is needed to evaluate the results of phr implementations. Their in-depth analysis of the literature signalled that there is little solid evidence from randomized controlled trials or other studies through the use of phr s. Hence, they suggested that more research is needed that addresses the current lack of understanding of optimal functionality and usability of these systems, and how they can play a beneficial role in supporting patient self-management ( Archer et al., 2011 ).

9.3.4. Forms of Aggregative Reviews

Healthcare providers, practitioners, and policy-makers are nowadays overwhelmed with large volumes of information, including research-based evidence from numerous clinical trials and evaluation studies, assessing the effectiveness of health information technologies and interventions ( Ammenwerth & de Keizer, 2004 ; Deshazo et al., 2009 ). It is unrealistic to expect that all these disparate actors will have the time, skills, and necessary resources to identify the available evidence in the area of their expertise and consider it when making decisions. Systematic reviews that involve the rigorous application of scientific strategies aimed at limiting subjectivity and bias (i.e., systematic and random errors) can respond to this challenge.

Systematic reviews attempt to aggregate, appraise, and synthesize in a single source all empirical evidence that meet a set of previously specified eligibility criteria in order to answer a clearly formulated and often narrow research question on a particular topic of interest to support evidence-based practice ( Liberati et al., 2009 ). They adhere closely to explicit scientific principles ( Liberati et al., 2009 ) and rigorous methodological guidelines (Higgins & Green, 2008) aimed at reducing random and systematic errors that can lead to deviations from the truth in results or inferences. The use of explicit methods allows systematic reviews to aggregate a large body of research evidence, assess whether effects or relationships are in the same direction and of the same general magnitude, explain possible inconsistencies between study results, and determine the strength of the overall evidence for every outcome of interest based on the quality of included studies and the general consistency among them ( Cook, Mulrow, & Haynes, 1997 ). The main procedures of a systematic review involve:

  • Formulating a review question and developing a search strategy based on explicit inclusion criteria for the identification of eligible studies (usually described in the context of a detailed review protocol).
  • Searching for eligible studies using multiple databases and information sources, including grey literature sources, without any language restrictions.
  • Selecting studies, extracting data, and assessing risk of bias in a duplicate manner using two independent reviewers to avoid random or systematic errors in the process.
  • Analyzing data using quantitative or qualitative methods.
  • Presenting results in summary of findings tables.
  • Interpreting results and drawing conclusions.

Many systematic reviews, but not all, use statistical methods to combine the results of independent studies into a single quantitative estimate or summary effect size. Known as meta-analyses , these reviews use specific data extraction and statistical techniques (e.g., network, frequentist, or Bayesian meta-analyses) to calculate from each study by outcome of interest an effect size along with a confidence interval that reflects the degree of uncertainty behind the point estimate of effect ( Borenstein, Hedges, Higgins, & Rothstein, 2009 ; Deeks, Higgins, & Altman, 2008 ). Subsequently, they use fixed or random-effects analysis models to combine the results of the included studies, assess statistical heterogeneity, and calculate a weighted average of the effect estimates from the different studies, taking into account their sample sizes. The summary effect size is a value that reflects the average magnitude of the intervention effect for a particular outcome of interest or, more generally, the strength of a relationship between two variables across all studies included in the systematic review. By statistically combining data from multiple studies, meta-analyses can create more precise and reliable estimates of intervention effects than those derived from individual studies alone, when these are examined independently as discrete sources of information.

The review by Gurol-Urganci, de Jongh, Vodopivec-Jamsek, Atun, and Car (2013) on the effects of mobile phone messaging reminders for attendance at healthcare appointments is an illustrative example of a high-quality systematic review with meta-analysis. Missed appointments are a major cause of inefficiency in healthcare delivery with substantial monetary costs to health systems. These authors sought to assess whether mobile phone-based appointment reminders delivered through Short Message Service ( sms ) or Multimedia Messaging Service ( mms ) are effective in improving rates of patient attendance and reducing overall costs. To this end, they conducted a comprehensive search on multiple databases using highly sensitive search strategies without language or publication-type restrictions to identify all rct s that are eligible for inclusion. In order to minimize the risk of omitting eligible studies not captured by the original search, they supplemented all electronic searches with manual screening of trial registers and references contained in the included studies. Study selection, data extraction, and risk of bias assessments were performed inde­­pen­dently by two coders using standardized methods to ensure consistency and to eliminate potential errors. Findings from eight rct s involving 6,615 participants were pooled into meta-analyses to calculate the magnitude of effects that mobile text message reminders have on the rate of attendance at healthcare appointments compared to no reminders and phone call reminders.

Meta-analyses are regarded as powerful tools for deriving meaningful conclusions. However, there are situations in which it is neither reasonable nor appropriate to pool studies together using meta-analytic methods simply because there is extensive clinical heterogeneity between the included studies or variation in measurement tools, comparisons, or outcomes of interest. In these cases, systematic reviews can use qualitative synthesis methods such as vote counting, content analysis, classification schemes and tabulations, as an alternative approach to narratively synthesize the results of the independent studies included in the review. This form of review is known as qualitative systematic review.

A rigorous example of one such review in the eHealth domain is presented by Mickan, Atherton, Roberts, Heneghan, and Tilson (2014) on the use of handheld computers by healthcare professionals and their impact on access to information and clinical decision-making. In line with the methodological guide­lines for systematic reviews, these authors: (a) developed and registered with prospero ( www.crd.york.ac.uk/ prospero / ) an a priori review protocol; (b) conducted comprehensive searches for eligible studies using multiple databases and other supplementary strategies (e.g., forward searches); and (c) subsequently carried out study selection, data extraction, and risk of bias assessments in a duplicate manner to eliminate potential errors in the review process. Heterogeneity between the included studies in terms of reported outcomes and measures precluded the use of meta-analytic methods. To this end, the authors resorted to using narrative analysis and synthesis to describe the effectiveness of handheld computers on accessing information for clinical knowledge, adherence to safety and clinical quality guidelines, and diagnostic decision-making.

In recent years, the number of systematic reviews in the field of health informatics has increased considerably. Systematic reviews with discordant findings can cause great confusion and make it difficult for decision-makers to interpret the review-level evidence ( Moher, 2013 ). Therefore, there is a growing need for appraisal and synthesis of prior systematic reviews to ensure that decision-making is constantly informed by the best available accumulated evidence. Umbrella reviews , also known as overviews of systematic reviews, are tertiary types of evidence synthesis that aim to accomplish this; that is, they aim to compare and contrast findings from multiple systematic reviews and meta-analyses ( Becker & Oxman, 2008 ). Umbrella reviews generally adhere to the same principles and rigorous methodological guidelines used in systematic reviews. However, the unit of analysis in umbrella reviews is the systematic review rather than the primary study ( Becker & Oxman, 2008 ). Unlike systematic reviews that have a narrow focus of inquiry, umbrella reviews focus on broader research topics for which there are several potential interventions ( Smith, Devane, Begley, & Clarke, 2011 ). A recent umbrella review on the effects of home telemonitoring interventions for patients with heart failure critically appraised, compared, and synthesized evidence from 15 systematic reviews to investigate which types of home telemonitoring technologies and forms of interventions are more effective in reducing mortality and hospital admissions ( Kitsiou, Paré, & Jaana, 2015 ).

9.3.5. Realist Reviews

Realist reviews are theory-driven interpretative reviews developed to inform, enhance, or supplement conventional systematic reviews by making sense of heterogeneous evidence about complex interventions applied in diverse contexts in a way that informs policy decision-making ( Greenhalgh, Wong, Westhorp, & Pawson, 2011 ). They originated from criticisms of positivist systematic reviews which centre on their “simplistic” underlying assumptions ( Oates, 2011 ). As explained above, systematic reviews seek to identify causation. Such logic is appropriate for fields like medicine and education where findings of randomized controlled trials can be aggregated to see whether a new treatment or intervention does improve outcomes. However, many argue that it is not possible to establish such direct causal links between interventions and outcomes in fields such as social policy, management, and information systems where for any intervention there is unlikely to be a regular or consistent outcome ( Oates, 2011 ; Pawson, 2006 ; Rousseau, Manning, & Denyer, 2008 ).

To circumvent these limitations, Pawson, Greenhalgh, Harvey, and Walshe (2005) have proposed a new approach for synthesizing knowledge that seeks to unpack the mechanism of how “complex interventions” work in particular contexts. The basic research question — what works? — which is usually associated with systematic reviews changes to: what is it about this intervention that works, for whom, in what circumstances, in what respects and why? Realist reviews have no particular preference for either quantitative or qualitative evidence. As a theory-building approach, a realist review usually starts by articulating likely underlying mechanisms and then scrutinizes available evidence to find out whether and where these mechanisms are applicable ( Shepperd et al., 2009 ). Primary studies found in the extant literature are viewed as case studies which can test and modify the initial theories ( Rousseau et al., 2008 ).

The main objective pursued in the realist review conducted by Otte-Trojel, de Bont, Rundall, and van de Klundert (2014) was to examine how patient portals contribute to health service delivery and patient outcomes. The specific goals were to investigate how outcomes are produced and, most importantly, how variations in outcomes can be explained. The research team started with an exploratory review of background documents and research studies to identify ways in which patient portals may contribute to health service delivery and patient outcomes. The authors identified six main ways which represent “educated guesses” to be tested against the data in the evaluation studies. These studies were identified through a formal and systematic search in four databases between 2003 and 2013. Two members of the research team selected the articles using a pre-established list of inclusion and exclusion criteria and following a two-step procedure. The authors then extracted data from the selected articles and created several tables, one for each outcome category. They organized information to bring forward those mechanisms where patient portals contribute to outcomes and the variation in outcomes across different contexts.

9.3.6. Critical Reviews

Lastly, critical reviews aim to provide a critical evaluation and interpretive analysis of existing literature on a particular topic of interest to reveal strengths, weaknesses, contradictions, controversies, inconsistencies, and/or other important issues with respect to theories, hypotheses, research methods or results ( Baumeister & Leary, 1997 ; Kirkevold, 1997 ). Unlike other review types, critical reviews attempt to take a reflective account of the research that has been done in a particular area of interest, and assess its credibility by using appraisal instruments or critical interpretive methods. In this way, critical reviews attempt to constructively inform other scholars about the weaknesses of prior research and strengthen knowledge development by giving focus and direction to studies for further improvement ( Kirkevold, 1997 ).

Kitsiou, Paré, and Jaana (2013) provide an example of a critical review that assessed the methodological quality of prior systematic reviews of home telemonitoring studies for chronic patients. The authors conducted a comprehensive search on multiple databases to identify eligible reviews and subsequently used a validated instrument to conduct an in-depth quality appraisal. Results indicate that the majority of systematic reviews in this particular area suffer from important methodological flaws and biases that impair their internal validity and limit their usefulness for clinical and decision-making purposes. To this end, they provide a number of recommendations to strengthen knowledge development towards improving the design and execution of future reviews on home telemonitoring.

9.4. Summary

Table 9.1 outlines the main types of literature reviews that were described in the previous sub-sections and summarizes the main characteristics that distinguish one review type from another. It also includes key references to methodological guidelines and useful sources that can be used by eHealth scholars and researchers for planning and developing reviews.

Table 9.1. Typology of Literature Reviews (adapted from Paré et al., 2015).

Typology of Literature Reviews (adapted from Paré et al., 2015).

As shown in Table 9.1 , each review type addresses different kinds of research questions or objectives, which subsequently define and dictate the methods and approaches that need to be used to achieve the overarching goal(s) of the review. For example, in the case of narrative reviews, there is greater flexibility in searching and synthesizing articles ( Green et al., 2006 ). Researchers are often relatively free to use a diversity of approaches to search, identify, and select relevant scientific articles, describe their operational characteristics, present how the individual studies fit together, and formulate conclusions. On the other hand, systematic reviews are characterized by their high level of systematicity, rigour, and use of explicit methods, based on an “a priori” review plan that aims to minimize bias in the analysis and synthesis process (Higgins & Green, 2008). Some reviews are exploratory in nature (e.g., scoping/mapping reviews), whereas others may be conducted to discover patterns (e.g., descriptive reviews) or involve a synthesis approach that may include the critical analysis of prior research ( Paré et al., 2015 ). Hence, in order to select the most appropriate type of review, it is critical to know before embarking on a review project, why the research synthesis is conducted and what type of methods are best aligned with the pursued goals.

9.5. Concluding Remarks

In light of the increased use of evidence-based practice and research generating stronger evidence ( Grady et al., 2011 ; Lyden et al., 2013 ), review articles have become essential tools for summarizing, synthesizing, integrating or critically appraising prior knowledge in the eHealth field. As mentioned earlier, when rigorously conducted review articles represent powerful information sources for eHealth scholars and practitioners looking for state-of-the-art evidence. The typology of literature reviews we used herein will allow eHealth researchers, graduate students and practitioners to gain a better understanding of the similarities and differences between review types.

We must stress that this classification scheme does not privilege any specific type of review as being of higher quality than another ( Paré et al., 2015 ). As explained above, each type of review has its own strengths and limitations. Having said that, we realize that the methodological rigour of any review — be it qualitative, quantitative or mixed — is a critical aspect that should be considered seriously by prospective authors. In the present context, the notion of rigour refers to the reliability and validity of the review process described in section 9.2. For one thing, reliability is related to the reproducibility of the review process and steps, which is facilitated by a comprehensive documentation of the literature search process, extraction, coding and analysis performed in the review. Whether the search is comprehensive or not, whether it involves a methodical approach for data extraction and synthesis or not, it is important that the review documents in an explicit and transparent manner the steps and approach that were used in the process of its development. Next, validity characterizes the degree to which the review process was conducted appropriately. It goes beyond documentation and reflects decisions related to the selection of the sources, the search terms used, the period of time covered, the articles selected in the search, and the application of backward and forward searches ( vom Brocke et al., 2009 ). In short, the rigour of any review article is reflected by the explicitness of its methods (i.e., transparency) and the soundness of the approach used. We refer those interested in the concepts of rigour and quality to the work of Templier and Paré (2015) which offers a detailed set of methodological guidelines for conducting and evaluating various types of review articles.

To conclude, our main objective in this chapter was to demystify the various types of literature reviews that are central to the continuous development of the eHealth field. It is our hope that our descriptive account will serve as a valuable source for those conducting, evaluating or using reviews in this important and growing domain.

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  • Cite this Page Paré G, Kitsiou S. Chapter 9 Methods for Literature Reviews. In: Lau F, Kuziemsky C, editors. Handbook of eHealth Evaluation: An Evidence-based Approach [Internet]. Victoria (BC): University of Victoria; 2017 Feb 27.
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Literature Review: Conducting & Writing

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Literature review example: frequently asked questions, is the sample literature review real.

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As we discuss in the video, every literature review will be slightly different, depending on the university’s unique requirements, as well as the nature of the research itself. Therefore, you’ll need to tailor your literature review to suit your specific context.

You can learn more about the basics of writing a literature review here .

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The Open Access Thesis Database (OATD) is a good starting point. 

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  1. PDF Doing a Literature Review in Health

    Doing a Literature Review in Health33 This chapter describes how to undertake a rigorous and thorough review of the literature and is divided into three sections. The first section examines the two main types of review: the narrative and the systematic review. The second section describes some techniques for undertaking a comprehensive search,

  2. Literature Reviews

    1. Develop a Focused Question Consider the PICO Format: Population/Problem, Intervention, Comparison, Outcome Focus on defining the Population or Problem and Intervention (don't narrow by Comparison or Outcome just yet!) Example: "What are the effects of the Pilates method for patients with low back pain?" Tools & Additional Resources:

  3. PDF How to write a systematic literature review: a guide for medical students

    For the example, a search for investigating the efficacy of a neuroprotective drug: (drug-x OR drug-x-alternative-name(s) OR drug-x-alternative-spelling(s)) AND (stroke OR isch(a)emia OR isch(a)emic OR cerebrovascular accident OR encephalic vascular accident).

  4. PDF Example of Literature Review

    2.1 Approaches to EHR summarization Given the unmet and well-recognized need for comprehensive EHR summarization (Powsner and Tufte 1994; Payne 2000), many research groups have designed and evaluated clinical data summarizers. In this chapter, we sample summarization applications to highlight different features including seminal

  5. (PDF) Conducting a Literature Review in Health Research: Basics of the

    Background: Literature reviews play a significant role in healthcare practice. There are different types of reviews available depending on the nature of the research question and the extent of ...

  6. Performing a literature review

    Literature reviews are most commonly performed to help answer a particular question. While you are at medical school, there will usually be some choice regarding the area you are going to review. Once you have identified a subject area for review, the next step is to formulate a specific research question. This is arguably the most important ...

  7. Writing an Effective Literature Review

    A literature review can be an informative, critical, and useful synthesis of a particular topic. It can identify what is known (and unknown) in the subject area, identify areas of controversy or debate, and help formulate questions that need further research. There are several commonly used formats for literature reviews, including systematic reviews conducted as primary research projects ...

  8. PDF Writing a Literature Review

    Your introduction should give an outline of why you are writing the review, and why the topic is important. ü "the scope of the review — what aspects of the topic will be discussed. ü the criteria used for your literature selection (e.g. type of sources used, date range) ü the organisational pattern of the review" (Citewrite, 2016 ...

  9. Literature Reviews

    Literature Reviews. Meeting the review family: exploring review types and associated information retrieval requirements | Health Information and Libraries Journal, 2019. A typology of reviews: an analysis of 14 review types and associated methodologies | Health Information and Libraries Journal, 2009. Conceptual recommendations for selecting ...

  10. (PDF) Writing a Literature Review Research Paper: A step-by-step approach

    Analysing literature gives an overview of the "WHs": WHat has been reported in a particular feld or topic, WHo the key writers are, WHat are the prevailing theories and hypotheses, WHat questions ...

  11. How to Write an Evidence-Based Clinical Review Article

    Traditional clinical review articles, also known as updates, differ from systematic reviews and meta-analyses. Updates selectively review the medical literature while discussing a topic broadly ...

  12. PDF Review Article

    Review articles are of different types based on the purpose of the review and the research question to address12. In this brief article, we'll cover 8 major types of literature reviews. These are: literature review, critical review, scoping review, systematic review, meta-analysis, qualitative systematic review, realist review, and review of ...

  13. Ten Simple Rules for Writing a Literature Review

    Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications .For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively .Given such mountains of papers, scientists cannot be expected to examine in detail every ...

  14. Chapter 9 Methods for Literature Reviews

    Literature reviews play a critical role in scholarship because science remains, first and foremost, a cumulative endeavour (vom Brocke et al., 2009). As in any academic discipline, rigorous knowledge syntheses are becoming indispensable in keeping up with an exponentially growing eHealth literature, assisting practitioners, academics, and graduate students in finding, evaluating, and ...

  15. (PDF) Writing narrative style literature reviews

    (PDF) Writing narrative style literature reviews Writing narrative style literature reviews December 2015 Medical Writing 24 (4):230-235 Authors: Rossella Ferrari Independent medical...

  16. PDF Sample Literature Review

    Level allow 1 headings readers introduce to clearly. a new indicate thought, a new idea, section argument, within or the topic. review. Level 1 headings Each are helpful Level 1 Subheading should be because they allow readers flushed left on the page. to and clearly formatted indicate a in new ALL-.

  17. PDF LITERATURE REVIEWS

    2. MOTIVATE YOUR RESEARCH in addition to providing useful information about your topic, your literature review must tell a story about how your project relates to existing literature. popular literature review narratives include: ¡ plugging a gap / filling a hole within an incomplete literature ¡ building a bridge between two "siloed" literatures, putting literatures "in conversation"

  18. Literature Review: Conducting & Writing

    Literature Review Sample 2 Literature Review Sample 3 Have an exemplary literature review? Have you written a stellar literature review you care to share for teaching purposes? Are you an instructor who has received an exemplary literature review and have permission from the student to post? Please contact Britt McGowan at [email protected] for ...

  19. Literature Review Example (PDF + Template)

    The literature review opening/introduction section; The theoretical framework (or foundation of theory) The empirical research; The research gap; The closing section; We then progress to the sample literature review (from an A-grade Master's-level dissertation) to show how these concepts are applied in the literature review chapter. You can ...

  20. (Pdf) Literature Review in Research

    PDF | On Mar 13, 2019, Janeesh Janardhanan and others published LITERATURE REVIEW IN RESEARCH | Find, read and cite all the research you need on ResearchGate

  21. (PDF) Systematic Literature Review: Some Examples

    This report to evaluated like example five articles marked like systematic literature review in relation with high performance computational engineering systems, being hardware or software based ...