What is a Systematic Review?
“A systematic review attempts to collate all relevant evidences that fit pre-specified eligibility criteria to answer a specific research question. It uses explicit, systematic methods to minimize bias in the identification, selection, synthesis, and summary of studies. When done well, this provides reliable findings from which conclusions can be drawn and decisions made. Key Characteristics include:
- A clearly stated set of objectives with 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 (e.g., assessment of the risk of bias and confidence in cumulative estimates)
- Systematic presentation, and synthesis, of the characteristics and findings of the included studies.”
Moher, D., Shamseer, L., Clarke, M., Ghersi, D., Liberati, A., Petticrew, M., … PRISMA-P Group. (2015). Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement. Systematic Reviews, 4(1), 1. http://doi.org/10.1186/2046-4053-4-1
As the name implies, a systematic review is a systematic, methodical, and scientific approach for identifying and analyzing all relevant information and data related to a clinically important question. Systematic reviews are hard work. Most professionals follow the protocols and methodologies set forth either by the PRISMA Statement or the Institute of Medicine's Finding What Works in Health Care: Standards for Systematic Reviews (2011). If you are unfamiliar with these documents, it is strongly recommended that you familiarize yourself with these protocols so you understand the methodology and requirements involved with this type of research.
Performing a systematic review requires
- A significant time commitment. Plan to spend 6-12 months to complete the process and write your analysis.
- A team. This type of research is performed by a team and not an individual in order to reduce the possibility of bias.
- A protocol. There are very strict guidelines on how to conduct this type of research. Refer to the PRISMA Statement or the Institute of Medicine's Finding What Works in Health Care: Standards for Systematic Reviews (2011) to plan your approach. Your protocol will include:
- A documentation strategy. You will need to document each step of this detailed process for reporting purposes. Therefore you need a plan at the outset so team members know how to gather, share, review, and analyze the research.
- A comprehensive literature review. This process will take on average 40 hours tp complete. The IOM report recommends in standards 3.1.1 that you "Work with a librarian or other information specialist trained in performing systematic reviews to plan the search strategy" & 3.1.3 "Use an independent librarian or other information specialist to peer review the search strategy."
What is a Meta Analysis?
A precise definition of this very specific type of research publication is provided by The Cochrane Handbook for Systematic Reviews of Interventions, "the official document that describes in detail the process of preparing and maintaining Cochrane systematic reviews on the effects of healthcare interventions":
1.2.2 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).
Many systematic reviews contain meta-analyses. Meta-analysis is the use of statistical methods to summarize the results of independent studies (Glass 1976). By combining information from all relevant studies, meta-analyses can provide more precise estimates of the effects of health care than those derived from the individual studies included within a review (see Chapter 9, Section 9.1.3). They also facilitate investigations of the consistency of evidence across studies and the exploration of differences across studies."
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.