Evidence synthesis involves a broad spectrum of review types, and scoping review is one such method, which, true to its name, is an effective technique to “scope” a broad topic in a research field. Unlike other types of reviews, scoping reviews can map the essential concepts underpinning a field of study and clarify working definitions and/or the conceptual limits of a topic. (1)
Scoping reviews are defined as a “type of evidence synthesis that aims to systematically identify and map the breadth of evidence available on a particular topic, field, concept, or issue, often irrespective of source (i.e., primary research, reviews, non-empirical evidence) within or across particular contexts.” (2) Scoping reviews help investigate new evidence when it is unclear what further, more specific questions can be valuably addressed by a more detailed systematic review.
While systematic reviews attempt to collate empirical evidence on a focused research question, scoping reviews seek to present a descriptive overview of a diversified literature on a broad topic that includes a wider range of study designs and methodologies to provide a descriptive overview of the reviewed material without critically appraising individual studies or synthesizing evidence from different studies. (3)The methodology followed for scoping reviews is largely similar to that followed for a systematic reviews, and meta-analysis is generally not possible with scoping reviews due to the broad and non-specific nature of the review objectives.
Scoping reviews, undertaken before systematic reviews, help authors and researchers understand the type and volume of data, ensuring sufficient pertinent studies for the reviewers to assess and include. They also allow for identifying relevant outcomes and target groups or populations, e.g., for a specific intervention. The reviewers are then quickly familiarized with studies on the topic, which eventually avoids creating an “empty” review. Scoping reviews of this type can assist reviewers in developing and validating their a priori inclusion criteria and ensure that existing, relevant data can answer the questions raised by their subsequent systematic review. (4, 5)
Scoping reviews aim to identify gaps in current research and indicate areas requiring additional investigation. Scoping reviews also seek to estimate the prospective amount and scope of extant research literature (sometimes including ongoing research) as well as the present level of synthesis. A scoping review can be performed when there is little data on a topic, data are heterogeneous, or when there is little evidence and the evidence is still emerging or unclear. For instance, a scoping review explored the available evidence in the literature on the safety and efficacy of ivermectin and doxycycline as monotherapy and combination therapy in COVID-19 management, and concluded that the existing evidence the evidence is insufficient to either justify or refute the usage of these two drugs in COVID-19. (6) Such results would then help prospective researchers plan for systematic reviews in the topic with more specific objectives. Hence, scoping reviews can be performed before a detailed systematic review on a broad topic and be a precursor to systematic reviews. (3,5)
Scoping reviews can also create “policy maps,” which include finding and mapping information from policy papers and reports that govern practice in a particular domain. It can also be used to examine how research has been conducted and identify critical characteristics or factors in a field. (5) The PRISMA-ScR (Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews) checklist is a useful guideline for preparing and reporting scoping reviews. This document aims to assist researchers, decision-makers, and policymakers in establishing basic ideas and a better knowledge of critical factors and characteristics to report in scoping reviews. (7) Scoping reviews thus have an important role in evidence-based medicine, and can assist in summarising both known and unknown facts on a domain.
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- Munn Z, Peters MDJ, Stern C, et al. Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach. BMC Med Res Methodol. 2018 Nov 19;18(1):143. doi: 10.1186/s12874-018-0611-x.
- Munn Z, Pollock D, Khalil H, et al. What are scoping reviews? Providing a formal definition of scoping reviews as a type of evidence synthesis. JBI Evid Synth. 2022 Apr 1;20(4):950-952. doi: 10.11124/JBIES-21-00483.
- Pollock D, Peters MDJ, Khalil H, et al. Recommendations for the extraction, analysis, and presentation of results in scoping reviews. JBI Evid Synth. 2023 Mar 1;21(3):520-532. doi: 10.11124/JBIES-22-00123.
- Pham MT, Rajić A, Greig JD, et al. A scoping review of scoping reviews: advancing the approach and enhancing the consistency. Res Synth Methods. 2014 Dec;5(4):371-85. doi: 10.1002/jrsm.1123. Epub 2014 Jul 24.
- Peters MDJ, Godfrey C, McInerney P, et al. Chapter 11: Scoping Reviews (2020 version). In: Aromataris E, Munn Z (Editors). JBI Manual for Evidence Synthesis, JBI, 2020.
- Bhowmick S, Dang A, Vallish BN, Dang S. Safety and Efficacy of Ivermectin and Doxycycline Monotherapy and in Combination in the Treatment of COVID-19: A Scoping Review. Drug Saf. 2021 Jun;44(6):635-644.
- Tricco AC, Lillie E, Zarin W, et al. PRISMA Extension for Scoping Reviews (PRISMA-ScR): Checklist and Explanation. Ann Intern Med. 2018 Oct 2;169(7):467-473. doi: 10.7326/M18-0850. Epub 2018 Sep 4.