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Systematic and Systematic-like Reviews

What is a systematic review?

"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 6.1, 2020)

Systematic reviews have become crucial in the evidence-based practice of health care professionals particularly - often used as the basis for the creation of clinical guidelines. They are also increasingly being used in other disciplines such as psychology, education, sociology, environmental science, engineering and business management.

 Key characteristics of a systematic review include:

  • a clearly defined topic, with pre-defined eligibility criteria for studies
  • a systematic and reproducible search strategy
  • the critical appraisal of included studies
  • a synthesis and systematic presentation of the findings of the included studies

Not everybody is a proponent of the systematic review, and they are not to be undertaken by the faint-hearted. "The idea of a systematic review is a nonsense, and the sooner those advocates of it are tried at the International Court of Human Rights in the Hague (or worse still, sent for counselling), the better." (Rees, 2002).

It could be that a Critically Appraised Topic (CAT) or Scoping Review is more relevant for your purposes. However, even a narrative review should be undertaken with systematic rigour, so parts of this guide will still be useful depending on how far you go with your research.

NOTE: A Meta-analysis is a statistical way to combine quantitative data extracted from a systematic review. Every meta-analysis has a systematic review behind it, but not every systematic review results in a meta-analysis!

Rees, J. L. (2002). Two cultures? Journal of the American Academy of Dermatology, 46(2), 313-314. doi:10.1067/mjd.2002.120618

What's the difference between reviews?

Researchers, academics and librarians all use various terms to describe different types of literature reviews. Indeed there is often inconsistency between the ways the types are discussed. Here are a couple of simple explanations.

The image below describes common review types in terms of speed, detail, risk of bias and comprehensiveness:

Description of the differences between review types in image form

"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

 

The table below has been adapted from a widely used typology of fourteen types of reviews, (Grant & Booth, 2009).  Here are four of the most common types:

REVIEW TYPES DESCRIPTION APPROXIMATE TIMEFRAME NO. OF REVIEWERS
Systematic review Seeks to systematically search for, appraise and synthesise research evidence in order to aid decision-making and determine best practice. Systematic reviews can vary in their approach, and are often specific to the type of study: studies of effectiveness, qualitative research, economic evaluation, prevalence, aetiology or risk, diagnostic test accuracy and so on. 8 months to 2 years 2 or more
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. 2-8 weeks 1-2
Traditional (narrative) literature review A generic review which 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

For a more detailed list of review types, see:

Grant, M.J. & Booth, A. (2009).  A typology of reviews: An analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26(2), 91-108.  DOI: 10.1111/j.1471-1842.2009.00848.x

See also our Library Resource Guide, Literature Review.