A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. It uses explicit, systematic methods that are selected with a view to minimizing bias, thus providing more reliable findings from which conclusions can be drawn and decisions made (Antman 1992, Oxman 1993). The key characteristics of a systematic review are:
Statistical methods (meta-analysis) may or may not be used to analyze and summarize the results of the included studies. Meta-analysis refers to the use of statistical techniques in a systematic review to integrate the results of included studies. (Source: PRISMA)
Before embarking on a systematic review, perform a literature search to assess whether published systematic reviews and protocols have been written on the same topic. A few examples of databases to search for this purpose are provided below.
PROSPERO: an international database of registered systematic reviews and protocols in health and social care
Systematic review search: utilizing the Article types filter will limit to systematic reviews. Note: other types of reviews (e.g., literature review) may also be retrieved.
Activating the filter:
Protocol search: same filtered search as above plus AND protocol:
Note: this search technique is inexact and will possibly retrieve systematic reviews including studies employing other types of protocols, as indicated by viewing the abstract for result #1 above (not shown here).
Once it has been decided that a systematic review will be conducted, this may be the time to identify potential journals which may be the most relevant. Journal editors will judge a systematic review based upon various parameters, including how it may add value to the scientific knowledge base, change clinical practice, fit within the journals’ mission and whether it complies with a particular standard such as PRISMA or from the National Academy of Medicine. Familiarity with the publication’s “instructions to authors” may save time in this regard. The Journal of the American Medical Association provides an excellent example of formatting and recommendations for systematic reviews.
Producing a protocol as the “plan” for the systematic review is recommended, as it enhances communication between team members, reduces potential for bias, and provides the research community with an informed view of the eventual systematic review process, if published. Guidance for formatting a protocol can be found below.
PRISMA-P: Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols
Why register a systematic review:
A team discussion on whether the systematic review will be updated in the future is helpful. Currently, there seems to be no consensus on when and how this process should be accomplished. Some brief points to consider are: