What is a scoping review? Steps, framework and example

Scoping reviewalso called a scoping study

A review that uses a planned, transparent search to map the research on a broad topic: how much there is, what kinds of evidence exist, what the key ideas are, and where the gaps lie.

The PRISMA website puts it in one line: scoping reviews "serve to synthesize evidence and assess the scope of literature on a topic". A scoping review does not try to prove that something works. It tells you what is out there.

The method is usually traced to a paper by Arksey and O'Malley, published in the International Journal of Social Research Methodology in 2005. They gave four reasons for doing one:

• to examine the extent, range and nature of the research on a topic
• to decide whether a full systematic review is worth doing
• to summarise and share what the research has found
• to identify gaps in the existing literature

A scoping review is also not limited to journal articles. University library guides describe it as covering a wider range of study designs than a systematic review usually allows. That mattered to Dhara, because much of what is known about children who care for family members sits in NGO reports and theses. Our blog on types of literature review compares the main review types side by side.

The clearest guidance comes from a paper by Zachary Munn and colleagues in BMC Medical Research Methodology in 2018. It lists six purposes that suit a scoping review:

1. to identify the types of available evidence in a given field
2. to clarify key concepts and definitions in the literature
3. to examine how research is conducted on a certain topic or field
4. to identify key characteristics or factors related to a concept
5. as a precursor to a systematic review
6. to identify and analyse knowledge gaps

Dhara could tick three of these at once. She did not know what types of evidence existed in India, or what the children were called: young carers, young caregivers or child caregivers. And she wanted the gaps, because one of them would become her PhD.

The same paper says when a scoping review is the wrong choice. If your question is about the feasibility, appropriateness, meaningfulness or effectiveness of a treatment or practice, a systematic review is likely the most valid approach. In simple words, "does it work?" is a systematic review question, and "what do we know?" is a scoping review question.

Both reviews follow a structured process and a search that others can repeat. The differences are in what they are for.

The row on quality surprises many students. Munn and colleagues explain that a scoping review does not aim to produce a critically appraised answer to a specific question, so risk of bias is generally not assessed. For the same reason, it cannot tell practitioners what to do.

When your guide asks "which framework are you following?", the answer is usually one of these.

Arksey and O'Malley (2005). The original framework has five stages, with an optional sixth:

1. identifying the research question
2. identifying relevant studies
3. study selection
4. charting the data
5. collating, summarising and reporting the results

The optional sixth is a consultation exercise with people who know the field.

Levac, Colquhoun and O'Brien (2010). This paper refined the framework stage by stage. It recommended two reviewers for study selection, and it argued that consultation should be a required stage and not an optional one.

JBI. The JBI Manual for Evidence Synthesis has a full chapter on scoping reviews. JBI guidance asks for a protocol written in advance and recommends the PCC mnemonic for the question.

PRISMA-ScR (2018). This is a reporting guideline, published by Tricco and colleagues in the Annals of Internal Medicine. It tells you what the written report must contain, not how to do the review.

1. Check that nobody has done it already.Search for published scoping reviews and protocols on your topic. Dhara found reviews on young carers in other countries, and none on India.
2. Frame the question with PCC.PCC stands for population, concept and context. It is looser than PICO on purpose, because a map needs a wide question.
3. Write a protocol.Set down the objectives, the eligibility criteria, a sample search strategy, how sources will be selected, how disagreements will be settled and the charting form.
4. Search widely.Use several databases, and add grey literature such as theses, conference proceedings and reports. Dhara searched Scopus, PubMed, Google Scholar, Shodhganga and NGO websites.
5. Screen in two stages.First titles and abstracts, then full texts, against the criteria in the protocol. Two people should screen independently, after trying the criteria on a small sample together.
6. Chart the data, then collate and report.These last steps have their own section below.

This is how the PCC looked for Dhara.

Her question became: "What is known from the existing literature about children under 18 who give unpaid care to a family member in India?"

University library guides suggest registering the protocol on the Open Science Framework (OSF) or Figshare, or publishing it in a journal such as JBI Evidence Synthesis. PROSPERO, the register many systematic reviewers use, is a different matter. Munn and colleagues noted in 2018 that it was not available for scoping reviews, and library guides still say the same, so check its current rules.

The search needed care, because the same children appear under different names. Dhara joined "young carer", "young caregiver" and "child caregiver" with OR before adding India. Our blog on searching academic databases shows how. She screened with Jignesh, a fellow scholar, and the protocol named Dr. Vaidya to settle any disagreement.

Charting is the scoping review word for data extraction. You fill the same form for every included source. Typical fields are the author, year, country, aim, population and sample size, method, and key findings. Dhara added two of her own: the word used for the children, and who they cared for.

Test the form on a few sources first. A literature review matrix is a good shape for the chart, with one source in each row.

The analysis is descriptive. You count, group and describe, without pooling numbers or ranking studies. Guides suggest a numerical summary together with a simple thematic analysis, shown in tables, charts or an evidence map. Here is the shape of Dhara's review.

The numbers are made up for this blog, but every box must add up in a real review too. Of the 32 sources, 19 were interview studies, 8 were surveys and 5 were reports from NGOs.

For the write up, follow PRISMA-ScR. Its checklist has 20 essential reporting items and 2 optional ones, running from the title and the protocol to the limitations and funding. The two items on critical appraisal of sources are worded "if done", which fits what we saw earlier: in a scoping review, appraisal happens only when the aim calls for it.

Guides on scoping reviews warn about the same few mistakes.

• choosing a scoping review only to avoid judging the quality of studies
• using it for a "does it work?" question that needs a systematic review
• setting the scope so wide that the screening never ends, or so thin that nothing useful is said
• ending with recommendations for practice or policy
• changing the plan midway without reporting the change and the reason
• assuming it will be quick

On the last point, the sources do not agree. One guide says a scoping review can often be done in a few months. One university library warns that it may take longer than a systematic review. It depends on how wide the question is, so plan the time with your guide.

Dhara's review took most of two semesters, and the map was worth it. The 32 sources used three different names for the same children. Only three had been done in villages. None had followed the children over time, and none had used school attendance records. Every study that spoke about schooling relied on what the children remembered.

So the question she had parked came back, sharper than before. Her PhD will follow young carers in the villages of one district through a full school year, using attendance registers. "Now you know why it needs doing," Dr. Vaidya said, "and you can show it in one table."