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Scoping reviews

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Introduction

"...scoping reviews map key concepts underpinning a research area and the main sources and types of evidence available... undertaken as stand-alone projects where an area is complex or has not been reviewed comprehensively before...scoping reviews are often conducted to examine research activity, disseminate findings, identify gaps and/ or determine the value of conducting a full systematic review..." — Wilson et al, 2012

Scoping reviews are exploratory projects that systematically map literature on a broad topic, identifying key concepts, theories and sources of evidence. In order to build your understanding of the different review types, see Grant et al, 2009 and Reynen et al, 2017). You will also want to review the scoping reviews chapter in JBI's Manual for Evidence Synthesis, 2024 which provides a comprehensive framework for conducting a scoping review, and the 2005 seminal paper: Arksey H, O'Malley L. Scoping studies: Towards a methodological framework. International Journal of Social Research Methodology. 2005;8:19-32.

Scoping reviews aim to address broader, more complex, and exploratory research questions... [as opposed to] systematic reviews which are designed to answer precisely defined, narrow questions. Searching in the scoping review should be systematic. CIHR describes scoping reviews thus: "[they] entail the systematic selection, collection and summarization of existing knowledge in a broad thematic area." Scoping reviews are often conducted before full syntheses, and undertaken when feasibility of the research is considered to be a challenge, either because the relevant literature is thought to be vast and diverse (varying by methods, theoretical orientations and disciplines) and/or it is thought that little literature exists. In the scoping review, the same systematic, rigorous methodologies used in systematic reviews are used to find studies and extract data. Analyses and syntheses are part of every scoping review but the depth and type of analysis are different.

More guidance

Scoping reviews are commonly used to better understand phenomena and to evaluate where research on a topic has or has not been completed. Scoping reviews are often a first step in conducting a systematic review because they allow researchers to see where there are data points in the larger literature landscape. This is valuable for evaluating whether or not a systematic review is a feasible or viable option in some cases. Systematic reviews are commonly completed to show comparative effectiveness of some interventions and a meta-analysis is usually done in these types of studies. Scoping reviews entail the systematic selection, collection and summaries of existing knowledge to identify where there is sufficient evidence to conduct a full synthesis or where insufficient evidence exists and further primary research is necessary.

  • The scoping review has become increasingly popular as a form of knowledge synthesis. However, a lack of consensus on scoping review terminology, definition, methodology, and reporting limits the potential of this form of synthesis. In this article, we propose recommendations to further advance the field of scoping review methodology.

What is a scoping of a topic?

A scoping review (also scoping study) refers to a gathering of literature in a given policy or clinical area where the aims are to accumulate as much evidence as possible and map the results. Scoping reviews are a type of literature review that aims to provide an overview of the type, extent and quantity of research available on a given topic. By ‘mapping’ existing research, a scoping review can identify potential research gaps and future research needs, and do so by using systematic and transparent methods. The term ‘scoping review’ does not seem to have a commonly-accepted definition but several researchers such as Arksey & O’Malley, 2005, Anderson et al, 2008 and Davis, 2009 have attempted definitions. In 2010, Rumrill et al said that "...scoping reviews are efficient ways of identifying themes and trends in high-volume areas of scientific inquiry." Generally, a scoping review is an iterative process whereby existing literature is identified, examined and conceptually mapped, and where gaps are identified. Think of a scoping review as a first step in doing a systematic review or large study.

Given the "scope" of a scoping review, their aim is to establish what research has been published on specific topics and disciplinary areas (including reviews of policies, practices and research). The literature search in a scoping review should be as extensive as possible, and include a range of relevant databases, hand searches and attempts to identify unpublished literature. Often, the underlying aim of a scoping review is to explore the literature as opposed to answering specific questions. The scoping review should also include locating organizations and individuals that are relevant to the domain and what those groups have published. In the social sciences, scoping studies are performed at an initial stage of doing research (ie. program, project, process, or grant). Scoping reviews are used in some research areas to justify further investigation, time and resources.

In 2010, Levac et al built on Arksey and O’Malley's scoping review methodology (see appendix) and proposed a list of six (6) stages for those undertaking a scoping study:

Stage 1: clarifying and linking the purpose and research question (identifying the research question)
Stage 2: balancing feasibility with breadth and comprehensiveness of the scoping process
Stage 3: using an iterative team approach to selecting studies
Stage 4: extracting data
Stage 5: incorporating a numerical summary and qualitative thematic analysis, reporting results and considering implications of study findings to policy, practice, or research
Stage 6: incorporating consultation with stakeholders as a knowledge translation component of scoping

Lastly, they propose other considerations for scoping methodologies in order to support the advancement, application and relevance of scoping studies in health research. In 2013, Daudt et al updated both the Arksey and Levac frameworks for scoping reviews.

Features of a good scoping review

According to Grant and Booth (2009), there are some characteristic features of scoping reviews that can be used to distinguish them from other types of reviews:

  • Preliminary assessment of size and scope of available research literature
  • Aims to identify nature and extent of research evidence (usually including ongoing research)
  • Completeness of searching determined by time/scope constraints
  • May include research in progress
  • No formal quality assessment
  • Typically tabular with some narrative commentary
  • Characterizes quantity and quality of literature in themes, perhaps by study design and other key features
  • Attempts to specify a viable review

Pre-systematic review searching

Scoping studies or reviews are undertaken as distinct research projects, and as precursors to other types of research. However, a ScR may be requested prior to the systematic review or preparatory to costing research projects. The interpretation, methodology and expectations of ScRs are variable and suggest that conceptually, they are not well-understood or defined. The distinction between scoping as an integral preliminary process in the development of a research proposal or a formative, methodologically rigorous activity in its own right has not been examined. ScRs in medicine are slowly evolving; their strength lies in their ability to summarize a body of evidence for quick but accurate synthesis. As with other approaches to evidence synthesis a standardized approach is always welcome. Full literature searching aimed at retrieving a maximum number of relevant studies or articles in a given discipline starts with a scope of a topic.

The ScR process is iterative and helps to estimate the size of the biomedical literature in question and the costs of searching it thoroughly. Some health librarians have begun to offer their information retrieval skills because interdisciplinary topics increase the likelihood of time-consuming searching -- this may be important to know before a large-scale project can be undertaken. Arksey and O'Malley in 2005 outlined a methodological framework that identifies different types of scoping studies, and how these compare to systematic reviews.

Importance of librarian in scoping reviews (ScRs)

  • It's a good idea to consult a methodologist and librarian before undertaking a scoping review; a librarian can translate operational definitions of concepts/topics into robust search strategies;
  • A variety of approaches to find citations for scoping studies should be undertaken, and a librarian can help with databases, searching features in each (keywords, MESH terms, wildcard operators); interfaces and platform changes; selecting the most appropriate index, tool, or database;
  • The librarian will recommend keyword and wildcard searches to maximize recall (or sensitivity); some authors (Sandieson, 2006) promote ‘pearl harvesting’, 'snowballing' and finding seminal articles in the area;
  • Ramer (2005) recommends a similar process for websites called ‘site-ation’; a scoping of the literature means locating other systematic reviews and clinical trials on specific topics. Over time, results from searches provide focus (or refocus) to aid in direction of a research proposal. Scans of the literature may show a review exists in Cochrane or elsewhere and that there is no need to replicate what is available.
  • Scoping searches begin in the major biomedical databases such as MEDLINE, CINAHL, Google scholar and PsycINFO which are themselves refining processes; identifying major sources to be searched thoroughly in the second phase of the project is a part of the refinement process.
  • Identifying the most important sources of information to search may shift based on the research. Searching protocols may be recommend but need tracking, documentation and taking screenshots (in Google Scholar for example).
  • Searching in the top biomedical databases is not always sufficient as other resources, non-English materials and grey literature hidden in the deep web, may prove important.

References

Disclaimer

  • Note: Please use your critical reading skills while reading entries. No warranties, implied or actual, are granted for any health or medical search or AI information obtained while using these pages. Check with your librarian for more contextual, accurate information.
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