"Systematic reviews seek to collate evidence that fits pre-specified eligibility criteria in order to answer a specific research question. They aim to minimize bias by using explicit, systematic methods documented in advance with a protocol." (Cochrane Handbook Version 6.3, 2020)
Key characteristics of a systematic review include:
A systematic review might also include a meta-analysis: a statistical way to combine quantitative data extracted from a systematic review. Note that every meta-analysis has a systematic review behind it, but not every systematic review includes a meta-analysis!
It might be that a systematic review is not appropriate for your situation, and a Critically Appraised Topic (CAT), a scoping review, or a traditional narrative review might be more relevant to your purpose (see table below). But even a narrative review should be undertaken with systematic rigour, so parts of this guide should still be useful depending on the level and extent of your review.
Researchers, academics, and librarians all use various terms to describe different types of literature reviews, and there is often inconsistency in the ways the types are discussed. Here are a couple of simple explanations.
"Schematic of the main differences between the types of literature review" by Brennan, M. L., Arlt, S. P., Belshaw, Z., Buckley, L., Corah, L., Doit, H., Fajt, V. R., Grindlay, D., Moberly, H. K., Morrow, L. D., Stavisky, J., & White, C. (2020). Critically Appraised Topics (CATs) in veterinary medicine: Applying evidence in clinical practice. Frontiers in Veterinary Science, 7, 314. https://doi.org/10.3389/fvets.2020.00314 is licensed under CC BY 3.0
| REVIEW TYPE | DESCRIPTION | TIMEFRAME | NO. OF REVIEWERS |
|---|---|---|---|
| Traditional (narrative) literature review | Identifies and reviews published literature on a topic, which may be broad. Typically employs a narrative approach to reporting the review findings. Can include a wide range of related subjects. | 1 - 4 weeks | 1 |
| Rapid review | Assesses what is known about an issue by using a systematic review method to search and appraise research and determine best practice. | 2 - 6 months | 2 |
| Scoping review | Assesses the potential scope of the research literature on a particular topic. Helps determine gaps in the research. (See the page in this guide on Scoping reviews.) | 1 - 4 weeks | 1 - 2 |
| Systematic review | Seeks to systematically search for, appraise, and synthesise research evidence so as to aid decision-making and determine best practice. Can vary in approach, and is often specific to the type of study, which include studies of effectiveness, qualitative research, economic evaluation, prevalence, aetiology, or diagnostic test accuracy. | 8 months to 2 years | 2 or more |
| Umbrella review | Summarises and compiles results from multiple systematic reviews into one accessible and reusable document - also known as a review of reviews. | 8 months to 2 years | 2 or more |
Grant, M. J., & Booth, A. (2009). A typology of reviews: An analysis of 14 review types and associated methodologies. Health Information and Libraries Journal, 26(2), 91-108. https://doi.org/10.1111/j.1471-1842.2009.00848.x
See also the Library's Literature Review guide.
The following flowchart might help you decide what sort of review is appropriate for your needs and situation.
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