What Is a Scoping Review? Purpose, Steps and Evidence

A scoping review is a structured evidence synthesis that maps what research exists on a topic, how it has been conducted, and where the gaps sit. It answers questions shaped like "what has been studied and how" rather than "does this intervention work". Understanding what is a scoping review matters because the label is often used loosely for any broad literature search, when in practice the method has its own protocol expectations, search documentation standards and reporting guideline.

This guide is written for postgraduate researchers, clinician researchers, librarians and policy analysts who have a broad question, a messy and multidisciplinary body of literature, and a decision to make about which review design fits. By the end you should be able to judge whether your question suits a scoping approach, plan the stages in sequence, document a search that includes grey literature, and report the result in a way that reviewers and journal editors accept.

Two practical points get lost in most introductions to what is a scoping review. The first is that scoping is a decision tool as much as a publication: many teams run one specifically to work out whether a narrower quantitative synthesis is viable, and to size the screening workload before committing eighteen months to it. The second is that the absence of critical appraisal is a deliberate design feature, not a shortcut. Because you do not weight studies by quality, you cannot use the results to say one option outperforms another. That single constraint drives most of the reporting rules discussed below.

Throughout, the term scoping review is used in the sense set out by the JBI methodology and the PRISMA-ScR reporting extension, which together describe the stages most journals now expect. If your question is narrow, comparative and already well defined, a different design will serve you better, and our systematic review guide covers that path. If you are still working out what the field contains, keep reading.

Key takeaways

• A scoping review maps the size, range and characteristics of the evidence on a broad topic, rather than pooling results to answer a single narrow effectiveness question.
• Choose this design when the literature is scattered across disciplines, when key concepts are still being defined, or when you need to know whether a full review is even feasible.
• Scoping reviews follow a published protocol, transparent search documentation and a structured charting process, so they are far more rigorous than an informal reading of the field.
• Reporting follows the PRISMA extension for scoping reviews (PRISMA-ScR), which expects a flow diagram, a charted data table and a clear statement that no critical appraisal or pooled effect estimate was produced.
• Findings are descriptive by design, so a scoping review sits outside traditional levels-of-evidence hierarchies and should not be used to make treatment recommendations.

What Is What Is a Scoping Review?

The clearest way to define what is a scoping review is to place it beside the alternatives on the features that actually change your workload: the shape of the question, whether you appraise study quality, and what the output looks like. A scoping review keeps a broad question, skips formal critical appraisal, and produces a descriptive map. That combination explains why it can include forty study designs at once, and why it cannot produce a pooled estimate.

Two consequences follow. Because appraisal is out of scope, a poorly conducted trial and a well conducted one appear as equal points on your map, so the map describes activity rather than reliability. And because the question stays broad, inclusion decisions are usually iterative: teams refine eligibility once they see what the search returns, which is acceptable in this design provided every change is dated and reported. Our design comparison tool and the key differences article go further into the boundary cases.

When Should You Choose a Scoping Review Over Other Methods?

Choose this design when at least one of four conditions holds. First, the concept itself is contested, so you need to see how authors define and operationalise it before you can specify eligibility criteria. Second, the literature spans disciplines with different vocabularies and publication habits, which makes a single tight search string unworkable. Third, you need a feasibility answer: how many records exist, what designs dominate, and whether a narrower synthesis would find enough comparable studies. Fourth, a funder or clinical network wants a map of current activity to set a research agenda.

The decision also has resourcing consequences. A scoping review usually returns a larger record set than a tightly framed question, so screening effort rises even though appraisal effort falls. Teams frequently underestimate the charting stage, which is where extraction of study characteristics across heterogeneous designs becomes slow and inconsistent. Budget for a piloted charting form and a second reviewer on a sample.

Avoid this design when you already have a precise comparative question with an established outcome set, because reviewers will ask why you did not appraise the evidence. Avoid it too when a decision-maker needs a recommendation on a short deadline; a rapid review is built for that constraint. Answering what is a scoping review in your own protocol therefore means stating plainly what the map will and will not support.

Which Types of Evidence Can Scoping Reviews Include?

Breadth of source type is the defining strength here. A single map may include randomised trials, cohort and case control studies, qualitative research, mixed methods studies, economic analyses, clinical guidelines, policy documents, theses, conference abstracts, registry entries, government and agency reports, and practice descriptions. Editorials and commentary can be included where the aim is to map discourse rather than findings, provided you label them as such in the charted table.

Deciding what to admit is a trade-off rather than a free choice. Wide inclusion gives a truer picture of a field where practice runs ahead of published trials, which is common in digital health, implementation and public health topics. It also multiplies screening volume, introduces duplicate reporting between an abstract, a thesis chapter and a later journal article, and makes charting fields inconsistent because grey documents rarely report sample sizes or comparators.

Practical safeguards help. Pre-specify document types you will admit and exclude in the protocol, with a reason for each. Record language and date limits and justify them rather than applying them silently. Flag linked outputs from the same project so counts are not inflated. Anyone drafting a protocol and still asking what is a scoping review should treat this eligibility section as the place where breadth becomes defensible rather than accidental.

How to Plan and Conduct a Scoping Review Step by Step

What you need before you start. Assemble a team of at least two screeners plus a third person to resolve disagreements, secure librarian input on the search strategy, confirm database access, choose a reference and screening workspace, and register or publish your protocol on an open repository. Also agree who owns the charting form and who signs off changes to eligibility.

To conduct a scoping review, work through the stages in order and record decisions as you go:

1. Frame the question using a population, concept and context structure rather than a comparator-based frame.
2. Write and publish the protocol, stating objectives, eligibility criteria, search sources, charting fields and how you will present results.
3. Build the search with a librarian across databases relevant to each discipline involved, then translate the strategy for each platform and save the exact strings and dates.
4. Screen titles and abstracts in duplicate against the eligibility criteria, piloting on 50 to 100 records first to check agreement.
5. Screen full texts in duplicate and log a specific reason for every exclusion.
6. Chart the data using a piloted form covering study characteristics, design, setting, population, concept definitions and key findings.
7. Collate, summarise and report the results as counts, tables and a narrative that names the gaps.

Understanding what is a scoping review at the planning stage saves rework later, because the protocol is where you commit to the descriptive purpose. Consultation with clinicians, consumers or policy users is an optional final stage that strengthens interpretation.

How to Write Up and Report Scoping Review Findings

Report against the PRISMA extension for scoping reviews (PRISMA-ScR). It expects a structured abstract, a stated objective and review question, full eligibility criteria, the complete search strategy for at least one database, a record of the selection process, the charting process and the charted results. A flow diagram showing records identified, screened, assessed at full text and included is standard; our PRISMA guide covers the counting rules that trip teams up.

Structure the results around your map rather than study by study. Lead with descriptive counts, such as publication year, country, design and setting, then present the concept-level findings in a table that mirrors your charting fields. Use figures sparingly and only where they encode real values. Say explicitly that critical appraisal was not undertaken and that no pooled effect was estimated, then state what that means for interpretation.

The gap statement is where most write-ups underdeliver. Naming a gap is only useful if you specify what is missing: a population, an outcome, a setting, a design, or a definition. Deviations from the protocol should appear in the methods with dates and reasons, since iterative refinement is expected in scoping work but silent drift is not.

Documenting Grey Literature Searches and Hand Searching

Grey literature searching is where reproducibility usually breaks down, because website searches are not saved queries and results shift week to week. Keep a search log with one row per source, recording the source name and URL, the exact terms used, any filters or facets applied, the date searched, the number of results reviewed, and the number taken forward. Where a site caps or reorders results, state the stopping rule you applied, such as reviewing the first 100 hits sorted by relevance.

Cover the source categories that suit your topic: government and agency publication libraries, clinical guideline registries, trial registries, thesis repositories, professional association sites, and preprint servers. Targeted web searching can be included when documented the same way. Hand searching means checking the reference lists of included studies and screening the tables of contents of key journals across a defined period, and both need their own log entries with yields.

Because these methods are less systematic than database searching, report them as a separate strand in your flow diagram so readers can see how many included documents came from outside the databases. Store screenshots or PDFs of retrieved grey documents, since they are frequently moved or withdrawn before publication.

Managing Screening, Charting and Team Workflow in Practice

Volume is the practical challenge. A broad question can return several thousand records, so agree the workflow before the first record arrives. Deduplicate, then screen titles and abstracts in duplicate with conflicts routed to a third reviewer. Pilot on a shared sample and compare decisions; if agreement is poor, the eligibility criteria need rewriting rather than the screeners needing more effort. Our practical guide on how to screen studies covers the mechanics in more depth.

Charting deserves the same discipline as screening. Pilot the form on five to ten included studies, check that two people extract the same values, and only then chart at scale. Expect to add fields as you go, and record when each field was added so that earlier studies are revisited rather than left blank.

Tooling choices are a trade-off. Spreadsheets are flexible but lose the audit trail that reporting guidelines expect, while dedicated review platforms preserve decision histories and duplicate screening records at the cost of setup time. Semi-automated prioritisation can surface likely includes earlier in large sets, though it does not remove the need for human decisions. Systematicly is one such platform. Whatever you choose, keep counts reconcilable so the flow diagram matches your logs, and apply the same systematic record keeping to every stage.

Why Researchers Conduct Scoping Reviews: Mapping Evidence and Finding Gaps

Researchers run these reviews for four reasons that hold up in practice. They clarify how a concept is defined across a field, which is a prerequisite for writing usable eligibility criteria later. They size the evidence base, so a team can tell a funder how many comparable studies exist before proposing a narrower synthesis. They surface gaps precisely enough to justify a new primary study. And they give policy and clinical networks a current picture of activity across jurisdictions.

Tips and common mistakes.

• Do not appraise quality informally and then imply the better studies were weighted; either the review has no appraisal or it is a different design.
• Do not describe your output as showing what works. A scoping map shows what has been studied.
• Publish the protocol before screening starts, and date any later changes.
• Do not let the map end at counts; interpret what the pattern means for practice and for the next study.
• Do not treat grey literature as optional garnish. If you include it, document it to the same standard as your database searches.

Once the map is complete, the natural next step is either a targeted primary study or a narrower synthesis, and our meta-analysis guide sets out what the latter requires in terms of comparability.

Frequently asked questions

What is a scoping review in simple terms?

It is a transparent, protocol-driven survey of the literature that describes what research exists on a broad topic, what forms it takes, and where the holes are. Instead of asking whether one treatment beats another, it asks how many studies exist, who they involved, where they were done, what designs were used, and how key terms were defined. The output is a map and a set of charted tables, not a verdict.

What is the difference between a scoping review and a systematic review?

The differences are in question shape, appraisal and output. A systematic review starts from a narrow, pre-specified question, appraises the quality of every included study, and synthesises the findings into an answer. A scoping map keeps the question broad, includes many study designs, routinely omits critical appraisal, and reports descriptive patterns. Both require a published protocol, duplicate screening and transparent search reporting, so the scoping option is not the easier path; it is the one suited to an undefined field. If your question is already tight and comparative, follow the systematic review process instead.

How do I write a scoping review?

Work through the stages in sequence and write as you go. Frame the question around population, concept and context. Publish a protocol covering eligibility, sources and charting fields. Build and record the search with a librarian. Screen titles, abstracts and full texts in duplicate, logging exclusion reasons. Chart the data using a piloted form. Then collate the results as counts and tables, add a narrative that names specific gaps, and report against PRISMA-ScR including a flow diagram. Note protocol deviations with dates rather than absorbing them silently.

Can I do a scoping review by myself?

Solo work is possible but weaker, and many journals will question it. The stages that most need a second person are eligibility piloting, screening and charting, because single-reviewer screening misses eligible records and single-reviewer charting produces inconsistent fields. If you have no co-reviewer, mitigate the risk: ask a supervisor or librarian to independently screen a random sample of 10 to 20 per cent, document the agreement rate, and state the limitation in your write-up. Do not present a single-screener map as though it had duplicate verification.

What level of evidence is a scoping review?

It does not sit on the traditional levels-of-evidence hierarchy at all. Those hierarchies rank designs by their ability to answer effectiveness questions, from systematic reviews of randomised trials at the top down to expert opinion. Because a scoping map deliberately skips critical appraisal and does not synthesise effects, it cannot be graded on that scale. Its value is descriptive: it tells you what evidence exists and how it is distributed, which then informs which appraised synthesis or primary study is worth doing. Treat it as a planning and mapping output, and never as the basis for a treatment recommendation.