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Literature review methods

Tags: English, General

Which review is right for you?

Are you sure you're doing a 'systematic review'?

While all literature reviews can be done in a systematic way, not every literature review is performed according to a method within the 'systematic review' family.

For example, scoping and systematic reviews both aim to be comprehensive, transparent, unbiased, and reproduceable.  This is not always the case with the type of narrative literature review you might want to write for the background section of a scholarly article or the introductory chapter of a book.

IMPORTANT! Make sure that your research question and methodology match. In other words, one type of review is not better than another, and your research question may be answered best by a review type other than a systematic review.

  Narrrative literature review Scoping review Systematic review
Research question General discussion of topic Broad overview of topic Focused (narrow or clinical) question or hypothesis
Protocol (a priori) No Sometimes Yes
Literature search Not comprehensive Comprehensive to locate all relevant studies Comprehensive to locate all relevant studies
Inclusion criteria Undefined; usually only studies that support claims Explicit description of study types to be included Explicit description of study types to be included
Standardized data extraction No Yes Yes
Critical appraisal (assessment of risk of bias) No Sometimes; not required Yes
Number of reviewers Usually one Usually two or more Must be at least two


How do scoping and systematic reviews differ?

Scoping and systematic reviews share many of the same processes since they both use transparent and rigorous methods to comprehensively identify and analyze all the relevant literature to answer a research question. The main difference between the methods depends on what is the aim or purpose of the review.

Scoping reviews aim to:

  • map the body of literature on a topic area.
  • provide an overview of a potentially large and diverse body of literature pertaining to a broad topic.
  • provide a descriptive overview of the material and critical appraisal of individual studies does not have to be performed.

Systematic reviews aim to:

  • sum up the best available research on a specific question.
  • collate empirical evidence from a relatively smaller number of studies pertaining to a focused research question.
  • provide a synthesis of evidence from studies assessed for risk of bias.

Adapted from: Pham, M., Rajić, A., Greig, J., Sargeant, J., Papadopoulos, A., & McEwen, S. (2014). A scoping review of scoping reviews: advancing the approach and enhancing the consistency. Research Synthesis Methods, 5(4), 371–385.

Should I do a scoping or systematic review?

Scoping review:

  • when you lack a specific (clinical) question/hypothesis
  • when you are looking for a broad overview on a topic
  • to identify the type of evidence available in a given field
  • to clarify key concepts/definitions in the literature
  • to identfy key characteristics/factors related to a concept
  • as a precurser to a systematic review
  • to identify and analyze knowledge gaps

Systematic review:

  • when you have a specific (clinical) question that fits a framework like PICO, or you want to test a hypothesis
  • to uncover international evidence
  • to confirm current practice, address variations in practice, or identify new practices
  • to identify and inform future areas for research
  • to identify and investigate conflicting results
  • to produce statements to guide decision-making

Adapted from: Munn, Z., Peters, M., Stern, C., Tufanaru, C., McArthur, A., & Aromataris, E. (2018). Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach. BMC Medical Research Methodology, 18(1), 143–143.

What other review types are there?

There are many types of reviews, each with slightly different purpose and methodology. For example:

  • Mapping review: aims to identify gaps in the literature
  • Rapid review: narrow, quick search and assessment of very specific question
  • Umbrella review: review of systematic reviews

For details and examples of other review types, see the additional resources listed below.

Additional resources