Scoping reviews are similar to systematic reviews but are conducted for different reasons. Scoping reviews tend to focus on the nature, volume, or characteristics of studies rather than on the synthesis of published data.
Scoping reviews were developed in the early 2000s. Researchers saw the need for a review type that could be published that was less detailed than a systematic review but more detailed than a narrative (summary) review. These can be more speculative: Scoping a research area in order to highlight possible new research directions. These can also position researchers as potential “thought leaders” within areas and so are popular article types to write as they can garner high citation rates.
According to a research article on scoping reviews, “Researchers may conduct scoping reviews instead of systematic reviews where the purpose of the review is to identify knowledge gaps, scope a body of literature, clarify concepts or to investigate research conduct.” ((Munn, et al. 2018).
To date, no set methods for scoping reviews have been established. General guidelines have been published and are detailed below. Despite the lack of rules, scoping reviews must contain valid, transparent research methods. As with all research studies, the methods above all must be reproducible by other authors.
A scoping review is a relatively new research methodology. However, when performed correctly, it can contribute greatly to a research field.
What is a scoping review?
Scoping reviews are similar to systematic reviews, but they tend to focus on the nature, volume, or characteristics of studies or gaps in knowledge. In contrast, systematic reviews evaluate and synthesize data on a particular subject or question.
Scoping reviews are performed to “scope” a broad topic in a research field.
Daudt et al. (2013) suggested the following definition of scoping studies: “Scoping studies aim to map the literature on a particular topic or research area and provide an opportunity to identify key concepts; gaps in the research; and types and sources of evidence to inform practice, policymaking, and research.”
The purpose of a scoping review
According to Munn et al., 2018, “Scoping reviews are useful for examining emerging evidence when it is still unclear what other, more specific questions can be posed and valuably addressed by a more precise systematic review. They can report on the types of evidence that address and inform practice in the field and the way the research has been conducted.”
You may perform a scoping review when there is little data on a topic or when data are heterogeneous. This may be when evidence is still emerging or unclear. Thus, scoping reviews can be performed prior to a detailed systematic review on a topic.
For example, many scoping reviews have been conducted on COVID-19. This is because COVID-19 is a relatively new disease and data are still being collected.
What level of evidence is a scoping review?
Systematic reviews have the highest level of evidence of all research types.
Scopings reviews do not contain the level of detail of systematic reviews. They may have a higher risk of bias due to higher heterogeneity. Thus, their level of evidence is considered only moderate.
The benefit of scoping reviews is that they help map the literature on a specific topic. Additionally, they can inform future research and systematic reviews on that topic.
How to conduct a scoping review
In 2005, Arksey and O’Malley published a scoping review framework. Their framework has been modified over the years, but the concepts remain the same.
They proposed an iterative six-stage process:
(1) identify the research question (2) identify relevant studies (3) select studies (4) chart the data (5) collect, summarize and report the results (6 - optional) perform a consultation exercise
Over the years, this framework has been enhanced by researchers such as Daudt et al. (2013).
There is no consensus on the length of a scoping review. Reviews should be long enough to clearly present the results but should not contain irrelevant information.
Scoping review protocols
Several websites outlining the gold-standard reporting guidelines for scoping reviews exist. Additionally, a PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) checklist specifically for scoping reviews has been published. Click here to review the PRISMA checklist.
The general protocol for a scoping review is as follows:
- Review objective(s)
- Preliminary search details, if performed
- Explanation of the need for this review
- Eligibility criteria
Sample search strategy
- Explanation of the search approach
- Black and gray literature that was searched
- Reasons for including the literature
- Study selection process,
- Include an explanation of how disagreements between reviewers will be resolved
The table/form used for data extraction and an explanation of the form
- Presentation of results and data
- This may include text, tables, charts, figures, etc.
For additional information, Click here to see the Joanna Briggs Institue’s website on scoping reviews.
Scoping reviews versus other types of reviews
Many types of reviews exist. The most common are systematic reviews, scoping reviews, and narrative reviews. Narrative reviews are also called summary reviews. It can be hard to know which type of review to choose.
Systematic reviews are often accompanied by meta-analyses. The goal of a systematic review is to summarize existing data on a specific research question. For example, does nutritional status in infancy affect obesity risk in early childhood? Another way to think about this is researching research! Research studies included in a systematic review must meet specific criteria regarding methods, outcomes, sampling, etc.
Munn et al. (2018) notes that “According to the Cochrane handbook, 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.’”
Additionally, systematic reviews mostly focus on specific study types; for example, case-cohort studies, prospective studies, etc. Scoping reviews can summarize data from many different study types (Arksey and O’Malley, 2005).
Scoping reviews also aim to answer a research question. However, the question can be a bit more broad, and the inclusion criteria not as strict. For example, you can include multiple study types in a scoping review, while study types in systematic reviews are generally restricted. Scoping reviews still must use reproducible research methods, but the methodology is not as strict.
As noted in Munn et al. (2018), “Scoping reviews are similar to systematic reviews in that they follow a structured process, however they are performed for different reasons and have some key methodological differences.”
Narrative reviews (summary reviews)
Narrative reviews do not aim to answer a research question. Rather, they aim to summarize the available data on a topic in a descriptive format. Narrative reviews are more similar to literature reviews or book chapters than research papers.Generally, no methods need to be followed because you are “telling the story” of a particular topic.
See below for a quick summary of the components of all three review types:
|Scoping Reviews||Systematic reviews||Narrative reviews|
|Summarizes previous research on a topic||Yes||Yes||Yes|
|Includes data analysis methods||Yes||Yes||No|
|Identifies gaps in knowledge||Yes||Sometimes||No|
|Provides a broad overview of a topic||Yes||No||Yes|
|Provides a detailed synthesis of a research question||No||Yes||No|
|Has an established methodology||Yes||Yes||No|
|Has a high level of evidence||No (moderate)||Yes||No|
While scoping reviews may not be as detailed as systematic reviews, they play a beneficial role in the research landscape. Scoping reviews can help summarize known and yet unknown data on a specific topic. This is especially true for new research topics, such as new diseases or technologies.
If your research interests involve new frontiers, consider publishing a scoping review.
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