Methods for Research Evidence Synthesis: The Scoping Review Approach

Research evidence synthesis involves the aggregation of available information using well-defined and transparent methods to search, summarize, and interpret a body of literature, frequently following a systematic review approach. A scoping review is a relatively new approach to evidence synthesis and differs from systematic reviews in its purpose and aims.¹ The purpose of a scoping review is to provide an overview of the available research evidence without producing a summary answer to a discrete research question.² Scoping reviews can be useful for answering broad questions, such as “What information has been presented on this topic in the literature?” and for gathering and assessing information prior to conducting a systematic review.¹

In this issue of the Journal of Hospital Medicine, Fan et al. used a scoping review to identify information available in the literature on contributors to loss and theft of controlled drugs in hospitals and the safeguards that have been suggested to address these diversions.³ The authors followed Arksey and O’Malley’s framework for scoping reviews and the PRISMA-ScR (Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews) checklist in reporting findings.^2,4

Scoping reviews describe existing literature and other sources of information commonly include findings from a range of different study designs and methods.⁵ The broad scope of the collected information makes using formal meta-analytic methods difficult, if not impossible. Results of a scoping review often focus on the range of content identified, and quantitative assessment is often limited to a tally of the number of sources reporting a particular issue or recommendation. In contrast, systematic reviews commonly select the information sources by requiring specific study types, such as randomized controlled trials, and imposing quality standards, such as adequate allocation concealment, and place their emphasis on synthesizing data to address a specific research question. (Table) By focusing on specific studies, the synthesis component in a systematic review often takes the form of a meta-analysis in which the results of multiple scientific studies are combined to develop a summary conclusion, such as a common effect estimate, along with an evaluation of its heterogeneity across studies.

A scoping review can be a particularly useful approach when the information on a topic has not been comprehensively reviewed or is complex and diverse.⁶ Munn et al. proposed several objectives that can be achieved utilizing the scoping review framework, including identifying types of existing evidence in a given field, clarifying key concepts or definitions in the literature, surveying how research is conducted on a certain topic, identifying key characteristics related to a certain topic, and identifying knowledge gaps.¹ When choosing to use a scoping review approach, it is important that the objective of the review align with the review’s indication or purpose.