According to the Cochrane Library, "A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question." Researchers conducting systematic reviews use explicit methods aimed at minimizing bias, in order to produce more reliable findings that can be used to inform decision making. (Section 1.1)
The key characteristics of a systematic review are:
a clearly stated set of objectives with pre-defined eligibility criteria for studies;
an explicit, reproducible methodology;
a systematic search that attempts to identify all studies that would meet the eligibility criteria;
an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and
a systematic presentation, and synthesis, of the characteristics and findings of the included studies.
(Lasserson TJ, Thomas J, Higgins JPT. Chapter 1: Starting a review. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.3 [updated February 2022]. Cochrane, 2022. Available from www.training.cochrane.org/handbook.)
If you find a systematic review is not appropriate for your purposes, this guide provides a brief overview of several other types of reviews that may be more applicable (see “Other Review Types”).
A systematic review is a lengthy process and you should be sure you have the time to commit to the process. Completing the systematic review can take from 12-18 months or more!
It takes time to develop exhaustive and comprehensive searches and additional time to review the results. Large citation retrievals (many thousand!) are possible depending on the topic.
Estimated timeline for completing a Cochrane systematic review:
1 – 2 Preparation of protocol.
3 – 8 Searches for published and unpublished studies.
2 – 3 Pilot test of eligibility criteria.
3 – 8 Inclusion assessments.
3 Pilot test of ‘Risk of bias’ assessment.
3 – 10 Validity assessments.
3 Pilot test of data collection.
3 – 10 Data collection.
3 – 10 Data entry.
5 – 11 Follow up of missing information.
8 – 10 Analysis.
1 – 11 Preparation of review report.
12 – Keeping the review up-to-date.
Source: Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org.
Once you have determined a systematic review is the best option for your research needs, you are encouraged to thoroughly examine the review process outlined within the guide as well as the external resources provided.