Scoping Review

A scoping review is a type of evidence synthesis that systematically maps the key concepts, types of evidence, and gaps in research on a broad topic area. Unlike a systematic review, which aims to answer a specific question by appraising and synthesizing all relevant evidence, a scoping review aims to chart the existing literature, identify the scope and nature of available evidence, and clarify concepts or definitions. Scoping reviews are guided by the framework developed by Arksey and O'Malley and refined by Levac, Colquhoun, and O'Brien.

Before investing in a full systematic review, researchers often need to understand the landscape of available evidence. Scoping reviews provide this overview, revealing how much research exists on a topic, what study designs have been used, which populations have been studied, and where the gaps lie. They are particularly valuable for emerging or interdisciplinary topics where the evidence base is heterogeneous and the boundaries of the research area are not yet well defined. Scoping reviews can also identify whether a full systematic review is warranted and feasible.

Scoping reviews follow a structured process similar to systematic reviews but with some key differences. The research question is typically broader and more exploratory, often framed as "What is the nature and extent of evidence on...?" rather than "What is the effect of X on Y?" The search strategy is comprehensive, often spanning multiple databases and including grey literature.

Current JBI guidance asks for an a priori protocol that sets out the objectives, eligibility criteria and methods, but the process can be iterative: as the boundaries of the topic become clearer during the review, the criteria may be refined, provided each change is documented and explained in the report. Data extraction focuses on mapping the characteristics of the literature (study designs, populations, settings, key findings, and methodological approaches) rather than extracting specific outcome data for meta analysis. Critical appraisal of individual studies is generally not performed, because the aim is to map the evidence rather than to judge how trustworthy each result is: JBI guidance (2020) advises against it unless the review's aim requires it, and PRISMA-ScR treats it as an optional item, reported if done.

Results are presented in tables, charts, and narrative summaries that map the evidence landscape. One way to present results is a "gap map" showing which combinations of populations, interventions, and outcomes have been studied and which have not.

The PRISMA extension for Scoping Reviews (PRISMA-ScR, published in 2018, with an update in development) provides a reporting checklist of 20 essential and 2 optional items tailored to scoping reviews. The JBI (formerly the Joanna Briggs Institute) Manual for Evidence Synthesis also provides detailed methodological guidance for conducting scoping reviews.

Conduct a scoping review when the research question is broad and exploratory, when the goal is to map the evidence rather than synthesize specific effect estimates, or when the topic is emerging and the types of available evidence are unknown. Scoping reviews are appropriate as preliminary steps before a systematic review, for identifying research gaps to inform funding priorities, and for clarifying key concepts and definitions. Do not use a scoping review when the goal is to produce a quantitative estimate of treatment effects or when a focused clinical question needs a definitive answer, as these require a systematic review.

A common error is using a scoping review as a shortcut to avoid the rigor of a systematic review when a systematic review would be more appropriate for the research question. Another mistake is failing to follow a systematic process, treating the scoping review as an informal narrative review. Researchers sometimes skip the protocol or change the eligibility criteria during the review without documenting why, which makes the map hard to reproduce; others refuse any refinement even when the scope of the topic proves unclear. Finally, presenting scoping review results without a clear summary of the gaps identified reduces the review's value for guiding future research.

A research team conducts a scoping review to map the evidence on digital health interventions for older adults with multimorbidity. They search six databases and include 142 studies spanning 12 countries and 8 intervention categories (telehealth, mobile apps, remote monitoring, decision support, electronic medication management, patient portals, wearable devices, and social connectedness platforms). The results reveal that 70% of studies focus on telehealth and remote monitoring, while digital decision support and social connectedness platforms are underrepresented. Only 18% of studies include participants aged 80 and older. The review identifies these underexplored areas as priorities for future research.