There are many different types of literature reviews or knowledge syntheses, from the traditional narrative literature review to the rigorous meta-analysis, and each has its own methodology. It's important for you to make sure that your research question fits the type of review you are undertaking and that you follow the appropriate methodological guidelines.
“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.”
- Cochrane Library, About Cochrane Systematic Reviews and Protocols
What is a Systematic Review? by the Campbell Collaboration
A meta-analysis is a type of systematic review that has a statistical analysis of the data pooled from multiple studies that meet the inclusion criteria. Not all systematic reviews include meta-analysis, but all meta-analyses will include a systematic review of the evidence.
See: Crombie, Iain K., and Huw T. Davies. What is meta-analysis? (2nd Ed). (2009): 1-8.
Tricco AC, Lillie E, Zarin W, O'Brien KK, Colquhoun H, Levac D, et al. PRISMA Extension for Scoping Reviews (PRISMA-ScR): Checklist and Explanation. Ann Intern Med. [Epub ahead of print ] doi: 10.7326/M18-0850
A generic term for an article that provide a narrative summary of the literature on a given topic. It may or may not include a comprehensive search or quality assessment.
"Rapid reviews are a form of knowledge synthesis in which components of the systematic review process are simplified or omitted to produce information in a timely manner."
Khangura S, Konnyu K, Cushman R, Grimshaw J, Moher D. Evidence summaries: the evolution of a rapid review approach. Syst Rev. 2012 Feb 10;1:10.
Dobbins, M. Rapid Review Guidebook. Hamilton, ON: National Collaborating Centre for Methods and Tools. 2017
World Health Organization, Alliance for Health Policy and Systems Research. Rapid reviews to strengthen health policy and systems: a practical guide. 2017
Realist Review / Synthesis
A synthesis of complex social interventions to explore how contextual factors influence the link between intervention and outcome (summed up in the question "what works, how, for whom, in what circumstances and to what extent?")..."
Wong G, Greenhalgh T, Westhorp G, Buckingham J, Pawson R. RAMESES publication standards: realist syntheses. BMC Med. 2013 Jan 29;11:21.
Umbrella Review (A Review of Reviews)
A synthesis of the findings from systematic reviews on the same question. The analysis may be on the reviews or the studies within the reviews.