To Scope or Not to Scope?
Article Summary: Scoping vs. Systematic Reviews
By Carly Leggett
We’ve spent some time here at KnowledgeNudge defining and making the case for knowledge synthesis (check out Kate’s post Knowledge Synthesis is Core to KT) and talking to those who are experts in it (see our interview with Ahmed in Dealing with Bias and Asking the Right Questions), but now it’s time to look at how you can begin to apply knowledge synthesis to your own work.
A question we get asked all the time is “should I do a systematic review or a scoping review?” Enter the timely new article “Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach?” from Zachary Munn and colleagues. Recently published in the debate section of BMC Medical Research Methodology, this article describes the differences in indications (i.e. reasons) for undertaking the two distinct styles of review, with specific attention to when it is (and is not) appropriate to engage in a scoping review.
Defining the Terms
In this article, the authors broadly define systematic reviews as “a type of research synthesis that is conducted by review groups with specialized skills, who set out to identify and retrieve international evidence that is relevant to a particular question or questions, and to appraise and synthesize the results of this search to inform practice, policy and in some cases, further research.” They go on to note that the Cochrane handbook states that a systematic review “uses explicit, systematic methods that are selected with a view to minimizing bias, thus providing more reliable findings from which conclusions can be drawn and decisions made.”
Although there is no universally agreed upon definition of a scoping review, the authors indicate that “the general purpose for conducting scoping reviews is to identify and map the available evidence.” Similar to a systematic review, scoping reviews follow a structured process but often with a broader scope, and for different reasons. In this article, they set out to provide a clear road map to what those reasons might be.
Although the article primarily focuses on scoping reviews and systematic reviews, they do spend some time discussing the concept of traditional literature searches and reviews and how and where they differ from scoping reviews. See Table 1 (below) from the article for an excellent summary of the three methods.
Indications for Scoping and Systematic Reviews
The authors argue that although both types of review can be valid, rigorous, and warranted, the indications for when to use a scoping review have been inconsistent and confusing to date. The comparison below outlines the authors’ suggested implications for each style of review. Within the article, they delve further into each implication for a scoping review and provide examples for researchers considering the scoping approach.
When NOT to Choose a Scoping Review
The authors also spend time examining the misuse of scoping reviews and situations when they are not indicated. These include:
- As an alternative to a systematic review in order to avoid the critical appraisal stage of review and with hope that it will be the “easier” road forward [In follow up with our team of Knowledge Synthesis (KS) experts here at the George & Fay Yee Centre for Healthcare Innovation (CHI), they agree that unfortunately, this is the most common type of ‘evidence synthesis’ undertaken by those less familiar with systematic review methods and this has led to scoping reviews becoming a default step up from the traditional literature search. Additionally, (and possibly for good reason), most scoping reviews are never published and never result in further evidence syntheses (e.g. systematic reviews) on a topic. It seems that many researchers consider a scoping review enough to provide the evidence they require for a grant application or further research, without critically appraising what has been done by others or synthesizing that evidence to form a baseline on which to build.];
- In order to map the literature on a particular topic that does not need mapping; or
- As a way to investigate broad questions instead of investing time and effort required in crafting the more specific questions required of a systematic review.
For researchers struggling to determine whether a scoping or a systematic review is warranted, this article offers an excellent starting point for examining the motives and indications of the research in order to determine a path forward.
We would also like to highlight how critical it is for researchers to talk to experts who conduct a variety of evidence syntheses, beyond just scoping reviews, for their feedback and advice on methodology. Despite the growing recognition of the rigor that can and should be used for scoping reviews, the key differentiation is in the nature of the research question and teasing out those differences can be difficult. Supports such as the KS team here at CHI are available for this very purpose. Additionally, in response to the recent advancements in scoping review methodology, a new Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) extension has been created for this style of review. Check out the PRISMA-ScR checklist and add it to your scoping review toolkit.