A systematic review is just one type of evidence synthesis. It differentiates itself from these others in that it appraises the quality of included studies, provides a synthesis and often a meta-analysis of the literature, takes great pains to mitigate bias, and follows certain reporting standards and protocols. While systematic reviews are comprehensive and one of the most rigorous forms of evidence synthesis, they may not always be the best fit for your research.
Other evidence synthesis methods include, but are not limited to:
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Khangura, S., Konnyu, K., Cushman, R., Grimshaw, J., & Moher, D. (2012). Evidence summaries: The evolution of a rapid review approach. Systematic Reviews, 1(1), 10-10
Samnani, S. S., Vaska, M., Ahmed, S., & Turin, T. C. (2017). Review typology: The basic types of reviews for synthesizing evidence for the purpose of knowledge translation. Journal of the College of Physicians and Surgeons--Pakistan, 27(10), 635-641