Reviews: From Systematic to Narrative: Writing the Review

Characteristics of Included Studies

Review authors must decide which characteristics of the studies are likely to be relevant to users of the review. Review authors should, as a minimum, include the following in the ‘Characteristics of included studies’ table:

Methods: study design (stating whether or not the study was randomized), including, where relevant, a clear indication of how the study differs from a standard parallel group design (e.g. a cross-over or cluster-randomized design); duration of the study (if not included under Intervention). Note: the ‘Methods’ entry should not include measures of risk of bias; these should appear in a ‘Risk of bias’ table (see Chapter 8, Section 8.5).

Participants: setting; relevant details of health status of participants; age; sex; country. Sufficient information should be provided to allow users of the review to determine the applicability of the study to their population, and to allow exploration of differences in participants across studies.

Intervention: a clear list of the intervention groups included in the study. If feasible, sufficient information should be provided for each intervention to be replicated in practice; for drug interventions, include details of drug name, dose, frequency, mode of administration (if not obvious), duration (if not included under Methods); for non-drug interventions, include relevant considerations and components related to the intervention.

Outcomes: a clear list of either (i) outcomes and time -points from the study that are considered in the review; or (ii) outcomes and time-points measured (or reported) in the study. Study results should not be included here (or elsewhere in this table).

Notes: further comments from the review authors on aspects of the study that are not covered by the categories above. Note that assessments of risk of bias should be made in a ‘Risk of bias’ table.

It is possible to add up to three extra fields in the ‘Characteristics of included studies’ table. Where appropriate, review authors are recommended to use an extra field to provide information about the funding of each study.

 From Cochrane Handbook

You will improve the quality of your review by adhering to the standards below. Using the appropriate standard can reassure editors and reviewers that you have conscientiously carried out your review.

Institutes of Medicine Standards for Systematic Reviews

The IOM standards promote objective, transparent, and scientifically valid systematic reviews. They address the entire systematic review process, from locating, screening, and selecting studies for the review, to synthesizing the findings (including meta-analysis) and assessing the overall quality of the body of evidence, to producing the final review report.

The PRISMA Statement

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses. A 27-item checklist, PRISMA focuses on randomized trials but can also be used as a basis for reporting systematic review of other types of research, particularly evaluations of interventions. PRISMA may also be useful for critical appraisal of published systematic reviews although it is not a quality assessment instrument to gauge the quality of a systematic review.

Further Reading

Moher D, Liberati A, Tetzlaff J, Altman DG; PRISMA Group. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. PLoS Med. 2009 Jul 21;6(7):e1000097. Epub 2009 Jul 21. PubMed PMID: 19621072.  

Liberati A, Altman DG, Tetzlaff J, Mulrow C, Gøtzsche PC, Ioannidis JP, Clarke M, Devereaux PJ, Kleijnen J, Moher D. The PRISMA statement for reporting  systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. PLoS Med. 2009 Jul 21;6(7):e1000100. Epub 2009 Jul 21. PubMed PMID: 19621070.  Also published in the Annals of Internal Medicine, BMJ, and the Journal of Clinical Epidemiology.

MOOSE Guidelines (click on the PubMed PMID link to view the checklist that is part of the article)

Meta-analysis of Observational Studies in Epidemiology checklist contains specifications for reporting of meta-analyses of observational studies in epidemiology. Editors will expect you to follow and cite this checklist.  It refers to the Newcastle-Ottawa Scale for assessing the quality of non-randomized studies, a method of rating each observational study in your meta-analysis.

Stroup DF, Berlin JA, Morton SC, Olkin I, Williamson GD, Rennie D, Moher D, Becker BJ, Sipe TA, Thacker SB. Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis Of Observational Studies in Epidemiology (MOOSE) group. JAMA. 2000 Apr 19;283(15):2008-12. PubMed PMID: 10789670.

Preferred Reporting Items for Systematic Reviews and Meta-Analsis

Prisma Flow Chart

PRISMA Checklist

QUORUM (Quality of Reporting Meta-Analysis)   

Source: Sampson M., Campbell K., Ajiferuke i>, Moher D., Randomized controlled trials in pediatric complementary and alternative medicine: where can they be found?  BMC Pediatr 2003; 3(1):1.  http://www.biomedcentral.com/1471-2431/3/1

It is vital that each step in the review process be documented.  This is especially true of the search process.  Normally the librarian that performed the searches will keep detailed records of databases searched, search strategies used, limits applied, and records retrieved.  Why go to all this trouble?  One reason is transparency.  The readers of your review must be able to satisfy themselves that the review is not open to bias.  Another reason is reproducibility.  Again, your readers must be able to replicated what you did and arrive at the same results.  Also, your team or another review team should be able to repeat the search(es) to keep the review current by including new studies.

You must become comfortable with the fact that your review will be ongoing until you actually put all the finishing touches on your paper or thesis and, as they say in the newspaper business, put it to bed.  If you are doing a thesis or dissertation, be sure that you follow the guidelines set out by your professor, your department or the graduate school.  It may be helpful to look at other published thesis or dissertations to get a good feel for how they are organized, formatted and writing style.

It is important that your lit review has a logical and coherent structure and that this structure is clearly apparent to your audience.  Be sure to let your audience know from the start how your review is organized.  Remember that the way that you choose to organize will largely depend on the type of information that you have selected and it is no uncommon for a review to use a combination of structural approaches.

There are several ways to structure you literature review.  The type below are by no means the only way to structure your review.  You must choose an organization that makes the most logical sense to you and, more importantly, to your audience.

1. Chronological Organization: This method is an historical or developmental discussion of the research and the articles you have selected.
2. "Classic" Studies Organization: This method is a discussion or outline of the major writings regarded as significant in your area of study.  Remember to acknowledge those benchmark studies or articles in your area of research.
3. Topical or Thematic Organization: In this method you divide you research into sections representing the categories of conceptual subject for you topic.  You r discussion is then organized around these categories or subjects.
4. Inverted Pyramid Organization:  You start your reviews with a discussion of the related literature from a broad perspective.  Then you work you wan down to ever more specific studies which focus increasingly on the specific question of your research.

As mentioned in other parts of this guide, you will need to link the literature to your research question, demonstrating how it supports or extends the topic or the existing knowledge in your area.  Be sure to highlight the strengths, weaknesses and omissions of the literature, providing a critique of the research. 

Be certain that your perspective, position or standpoint is clearly identifiable in the literature review.  First, state your theoretical position clearly and strongly.  Second, it is important that your language indicates your own or other writers' attitudes to the question or issues. 

Below is a suggested outline for writing the results of your IRR.

References

Cooper, H. (1982). Scientific guidelines for conducting integrative research reviews. Review of Educational Research, 52, 291-302.

Cooper, H.M. (1989). Integrating research: A guide for literature reviews (2nd ed.). Newbury Park, CA: Sage Publications.

Cooper, H.M. (2001). Synthesizing Research: A guide for literature reviews (3rd ed.). Newbury Park, CA: Sage Publications.