Journal of Neurologic Physical Therapy: Fundamentals of a Systematic Review of the Literature

The purpose of a systematic review is to provide a balanced and unbiased synthesis of evidence related to a defined clinical question. The systematic review differs from a narrative review in that it applies a systematic approach to exploring the literature, assessing the strength of evidence, synthesizing the findings of individual studies, and interpreting the results.

The process and methods of the review must be transparent to the reader such that each of the critical steps are explicitly described.

Step 1: Define the Clinical Question

* What is the population of interest?

* What subpopulation(s) will be excluded?

* What is the intervention of interest?

* What outcomes are of interest?

Step 2: Explore the Literature

* What databases will be searched? (Bear in mind that less than one half of all clinical trials are published on MEDLINE.)

* Define the limits of the search (language, publication date, publication type, [eg, will conference proceedings or abstracts be included?]).

* Beware of publication bias against negative results (leading journals are more likely to publish results with positive effects compared with no effects or negative effects).

* Identify and read all potentially relevant studies.

Step 3: Assess the Strength of the Evidence

* Describe the reasons that studies were excluded from review.

* Characterize those studies that meet inclusion criteria.

* Assess the strength of the evidence and quality of the methods for each of the studies. (Note: There are several approaches for assessing the quality of research studies.1,2)

Step 4: Synthesizing the Findings

* Describe the quantitative (meta-analysis) or qualitative methods used to pool the results from the eligible studies.

* Describe how missing data were handled.

Step 5: Interpret the Results

* Describe the overall findings of the aggregate analysis.

* Provide a perspective on the results (describe strengths/weaknesses, issues of heterogeneity, potential bias).

* Make recommendations based on the strength of the evidence presented.

For a comprehensive guide to writing a systematic review, the reader is referred to the Cochrane Handbook.3 In addition, there are a number of excellent systematic reviews that have been published by the Cochrane Review Group that may serve as useful examples; these can be accessed at the Cochrane Library Web site.4

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