“A systematic review attempts to collate all relevant evidences that fits 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:
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.
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.