Scoping Review vs Systematic Review: How to Choose the Right Tool
Scoping reviews and systematic reviews are not interchangeable tools. Choosing the wrong one wastes resources at best and produces misleading conclusions at worst - and the misuse of scoping reviews to avoid rigour is a real pattern.
When Arksey and O'Malley published their framework for scoping studies in 2005, the field of evidence synthesis had a clear gap: there was no well-defined methodology for the kind of broad, exploratory mapping of a literature that researchers often needed to do before a systematic review was feasible or warranted. Their paper provided that framework, and it has been cited more than ten thousand times. What it also did, inadvertently, was give researchers who wanted to avoid the rigour of a systematic review a methodologically legitimate alternative that they could adopt without the full analytic commitment that a systematic review requires.
What Each Tool Is For
A systematic review is designed to answer a specific, well-defined question by exhaustively identifying, critically appraising, and synthesising all relevant evidence. It requires a formal protocol, a comprehensive search strategy, duplicate screening, quality appraisal using validated tools, and a synthesis that allows conclusions to be drawn about effect estimates or the strength of evidence supporting specific recommendations. It is the appropriate tool when the research question is specific enough to define eligibility criteria clearly, when sufficient primary studies are expected to exist, and when a definitive answer - or a definitive statement about the absence of one - is needed.
A scoping review is designed to map the extent, range, and nature of evidence on a topic. It is appropriate for broad questions, emerging fields, or heterogeneous evidence bases where a systematic review is premature. It can identify research gaps, clarify concepts, and describe the types of evidence available, but it is not designed to synthesise evidence in a way that supports definitive conclusions about effectiveness. A scoping review that reports conclusions about whether an intervention works is not doing what a scoping review is supposed to do - it is doing a systematic review poorly.
The JBI Framework
The Joanna Briggs Institute (JBI) has developed the most widely adopted contemporary framework for scoping reviews, updated from the Arksey and O'Malley original to incorporate methodological advances. The JBI framework specifies a five-stage process: formulating the research question; identifying relevant studies; selecting relevant studies; charting the data; and collating, summarising, and reporting results. Critically, it does not include formal quality appraisal of included studies as a required step - a feature that distinguishes it from systematic review methodology and reflects the exploratory, descriptive purpose of the scoping review.
The PRISMA-ScR (PRISMA extension for Scoping Reviews) checklist, published in 2018, provides reporting standards specific to scoping reviews, including items on the protocol, eligibility criteria, charting, and the description of what was not done (such as quality appraisal) and why. Adherence to PRISMA-ScR is increasingly expected by journals publishing scoping reviews.
The Misuse of Scoping Reviews
The proliferation of scoping reviews in the biomedical literature over the past decade has been accompanied by a troubling pattern: scoping reviews being published on questions that are specific enough to warrant a systematic review, by teams that either did not appreciate the distinction or chose the less demanding methodology deliberately. A scoping review that examines whether cognitive behavioural therapy reduces anxiety in adults - a specific, answerable question with decades of RCT evidence - is not being used appropriately. The label "scoping review" does not make the methodology appropriate; the research question does.
The consequence of misclassified scoping reviews is not just methodological imprecision - it is that readers and decision-makers consume what looks like an evidence synthesis and draw conclusions that the methodology does not support.
How to Decide Which You Need
A practical decision framework for choosing between the two tools starts with the research question. Is it specific enough to define PICO (Population, Intervention, Comparator, Outcome) components clearly? Is an answer about effectiveness, safety, or diagnostic accuracy the goal? If yes to both, a systematic review is likely appropriate. If the question is broader - what kinds of interventions exist for this condition? What study designs have been used in this area? What populations have been studied? - a scoping review is the right tool.
A second consideration is timing. A scoping review is often the right first step when entering an unfamiliar area - mapping what exists before designing the specific question that a systematic review will answer. In this sequence, the scoping review is not a substitute for the systematic review but a prerequisite for designing a better one.
Resource Considerations
The resource difference between a scoping review and a systematic review is real but sometimes overstated. A rigorous scoping review on a broad topic - with a comprehensive search, duplicate screening, and thorough data charting - can require comparable effort to a systematic review on a narrow topic. The distinction is not primarily about effort; it is about the analytical commitments that each methodology makes. Choosing a scoping review to save time on a question that warrants a systematic review is a false economy - it produces a document that cannot answer the question it addresses.
At NousLab, we help research teams make this decision explicitly, at the protocol stage, so that the methodology chosen is aligned with the question and the purpose. Talk to us about designing the right evidence synthesis for your question.
