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Systematic Review Overview: 7. Complete Data Analysis and Compile Results

Introduction to the 8 elements that encompass a systematic review
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Step 7: Complete Data Analysis and Compile Results

Quantitative Systematic Reviews

The strategy for the data analysis and compilation of the results will be driven by the research proposal or protocol, and the requirements of the agency to which the systematic review will be submitted. It should be known from the outset whether a meta-analysis is planned for the systematic review and the anticipated types of data analyses that will be required.

The protocol should also outline how heterogeneity will be explored and quantified, under what circumstances a meta-analysis would be considered appropriate, and whether a fixed or random-effects model or both would be used. Where appropriate, the approach to narrative synthesis should also be outlined. The protocol should also specify the outcomes of interest and what effect measures will be used. (Centre for Reviews and Dissemination. Systematic Reviews: CRD's guidance for undertaking systematic reviews [PDF file]. York, UK: Centre for Reviews and Dissemination, University of York; 2009 [cited May 22, 2009] See Chapter 1, Section 1.2: The Review Protocol.)

An excellent summary of the process is described in the book, Systematic Reviews : CRD’s guidance for undertaking reviews in health care, January 2009, and follows here:

Summary: Data synthesis

  • Synthesis involves bringing the results of individual studies together and summarising their findings.
  • This may be done quantitatively or, if formal pooling of results is inappropriate, through a narrative approach.
  • Synthesis should also explore whether observed intervention effects are consistent across studies, and investigate possible reasons for any inconsistencies.

Initial descriptive synthesis

All syntheses should begin by constructing a clear descriptive summary of the included studies.

Narrative synthesis is frequently an essential part of a systematic review, and as with every other stage of the process, bias must be minimized. Narrative synthesis has typically not followed a strict set of rules. However, a general framework can be applied in order to help maintain transparency and add credibility to the process. The four elements of this framework are:

  • Developing a theory of how the intervention works, why and for whom
  • Developing a preliminary synthesis of findings of included studies
  • Exploring relationships within and between studies
  • Assessing the robustness of the synthesis

Each element contains a range of tools and techniques that can be applied. A researcher is likely to move iteratively among the four elements, choosing those tools and techniques that are appropriate to the data being synthesised and providing justifications for these choices.