# How to Write a Scoping Review Protocol ## Quick Answer - Use the PRISMA-ScR reporting guideline as your structural checklist when drafting a scoping review protocol, and register the protocol before data extraction begins. - Build your protocol around six mandatory elements: eligibility criteria, information sources, search strategy, selection process, data charting process, and data items. - A protocol is a living planning document, not a binding contract, but deviations from it must be documented and reported transparently in the final review. ## What Is a Scoping Review Protocol A scoping review protocol is a written plan that specifies how you will conduct a scoping review before you begin the work. It documents the research question, the sources you will search, the criteria for including and excluding studies, and the methods you will use to extract and present findings. The protocol serves as a public record of your intended methods, which allows readers to assess the rigor of your review and to distinguish planned methods from post hoc decisions. Scoping reviews differ from systematic reviews in purpose and output. A systematic review answers a focused question by synthesizing evidence from studies that meet strict eligibility criteria. A scoping review maps the existing literature on a broader topic, identifies gaps, clarifies key concepts, and examines how research is conducted in a particular field. Scoping reviews are common in biology and environmental science when researchers want to understand the range of evidence on a topic such as pollinator decline, microplastic contamination, or the effects of agricultural runoff on aquatic ecosystems. The protocol is not the same as the final review report. The protocol describes what you plan to do. The final report describes what you actually did, including any changes from the plan. The [EQUATOR Network](https://www.equator-network.org/) maintains a library of reporting guidelines that help authors select the appropriate standard for their study type. For scoping reviews, the relevant guideline is PRISMA-ScR, which stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. ## Why a Protocol Matters for Scoping Reviews A written protocol protects the integrity of your review in several concrete ways. First, it forces you to clarify your research question before you invest time in searching. A vague question produces a vague search strategy and an unmanageable set of results. Second, it reduces the risk of selective reporting. When you document your eligibility criteria in advance, you are less likely to unconsciously favor studies that support a particular viewpoint. Third, it allows others to evaluate your methods. Reviewers, funders, and readers can compare your final report against your protocol to see where and why you deviated. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) core practices emphasize the importance of transparent research conduct. While these practices focus on authorship, peer review, and data integrity, the underlying principle applies to protocol development. A protocol that is vague, internally inconsistent, or written after the review is complete undermines the credibility of the entire project. For researchers seeking funding, a protocol is often a required component of a grant application. The [NIH Grants and Funding](https://grants.nih.gov/) portal describes the application and review process for NIH-supported research. While not every scoping review requires NIH funding, the expectation of rigorous planning applies across funding sources. A well-written protocol demonstrates that you have thought through the feasibility of your project and that you have a plan for managing the volume of literature you will encounter. ## At a Glance | Protocol Element | What You Document | Common Mistake | | --- | --- | --- | | Research question | The precise question your review will answer, often framed using PCC (Population, Concept, Context) | Writing a question that is too broad to search effectively | | Eligibility criteria | The characteristics that determine which studies are included or excluded | Listing criteria that are vague or that cannot be applied consistently | | Search strategy | The databases, search terms, and filters you will use | Searching only one database or failing to document the full strategy | | Study selection | The process for screening titles, abstracts, and full texts | Having one person screen all records without a second reviewer | | Data charting | The form you will use to extract information from included studies | Extracting data without a pilot-tested form | | Data synthesis | How you will collate, summarize, and present the findings | Attempting a statistical meta-analysis in a scoping review | ## Core Principles of Protocol Writing ### Transparency A protocol exists to make your methods visible to others. Every decision that affects which studies enter your review should be documented. This includes the databases you will search, the date range you will cover, the language restrictions you will apply, and the criteria you will use to determine eligibility. If you plan to hand-search reference lists or contact experts for unpublished literature, document that plan as well. ### Reproducibility Another researcher should be able to follow your protocol and obtain results that are substantially similar to yours. This requires specificity. Instead of writing "we will search relevant databases," write "we will search PubMed, Web of Science, and Scopus from January 2000 to December 2024 using the search string in Appendix A." The [National Library of Medicine](https://www.ncbi.nlm.nih.gov/books) hosts research-methods references that can help you understand the level of detail expected in biomedical and life-science research planning. ### Feasibility A protocol that cannot be executed is worse than no protocol at all. Before you finalize your protocol, test your search strategy in one database and count the results. If your search returns 50,000 records, your eligibility criteria are likely too broad or your question is too wide. If it returns 15 records, you may be missing key search terms or relevant databases. Adjust your protocol before you commit to the full search. ### Flexibility Within Limits Scoping reviews are iterative by nature. You may discover new concepts or terms as you screen the literature. The protocol should acknowledge that refinements are possible, but it should also specify how you will document those refinements. A common approach is to record all changes in a version log or an amendment table that accompanies the protocol. ## Core Elements of a Scoping Review Protocol ### Title and Registration Information The protocol should begin with a descriptive title that identifies the review as a scoping review. Include the names and affiliations of all authors, the date of the protocol, and a version number. If you plan to register the protocol, include the registration platform and the registration number. Registration is not mandatory for scoping reviews, but it provides a public timestamp that demonstrates your methods were established before the review began. ### Background and Rationale The background section explains why the scoping review is needed. Describe the current state of knowledge on your topic, identify the gaps or ambiguities that the review will address, and explain how the review will contribute to the field. This section should be concise but specific. Avoid broad statements about the importance of your topic and focus instead on the specific evidence gap your review will fill. ### Research Question and Objectives State your research question explicitly. For scoping reviews, the PCC framework is commonly used: - Population: the participants, organisms, or systems of interest - Concept: the intervention, exposure, phenomenon, or outcome of interest - Context: the setting, geographic scope, or other contextual factors For example, a scoping review in environmental science might ask: "What is known about the effects of neonicotinoid pesticides on non-target insect populations in agricultural landscapes in North America?" Here, the population is non-target insects, the concept is neonicotinoid exposure and its effects, and the context is agricultural landscapes in North America. List your specific objectives as numbered statements. Each objective should be achievable and should map to a section of your results. ### Eligibility Criteria Eligibility criteria define which studies will be included and excluded. Organize them into inclusion criteria and exclusion criteria. Common criteria include: - Study design (e.g., empirical studies, reviews, gray literature) - Publication date - Geographic location - Language - Population or subject characteristics - Type of outcome or concept reported Be specific. Instead of "studies on water quality," write "studies reporting quantitative measurements of nitrate, phosphate, or dissolved oxygen concentrations in freshwater systems." The [EQUATOR Network](https://www.equator-network.org/) guidance on reporting transparency can help you understand how detailed your criteria should be to support clear reporting. ### Information Sources List every source you will search. This includes bibliographic databases such as PubMed, Web of Science, Scopus, and Embase, as well as gray literature sources such as government reports, thesis repositories, and organizational websites. For each source, specify the date range you will cover and any limits you will apply. If you plan to search trial registries or preprint servers, list them here. ### Search Strategy The search strategy is the most technically demanding part of the protocol. It should include: - The full search string for at least one major database - The list of search terms and their variants - Any filters or limits you will apply - The date the search will be run Develop your search strategy in consultation with a librarian or information specialist if possible. Test the strategy in one database, review the results for relevance, and refine the terms before finalizing the protocol. Document the development process so readers can see how the final strategy was derived. ### Study Selection Process Describe how you will screen the records identified by your search. Specify: - How many reviewers will screen titles and abstracts - Whether screening will be done independently or in duplicate - How disagreements will be resolved - Whether full-text screening will follow the same process A common approach is to have two reviewers screen all titles and abstracts independently, resolve disagreements by discussion or by a third reviewer, and then screen full texts using the same process. Document the proportion of records that will be double-screened if you plan to use a single reviewer for part of the process. ### Data Charting Process Data charting is the scoping review equivalent of data extraction in a systematic review. Describe the form you will use to collect information from each included study. Specify: - Who will extract the data - Whether extraction will be done in duplicate - How disagreements will be resolved - Whether the form will be pilot-tested The data charting form typically collects bibliographic information, study characteristics, and findings relevant to your research question. A pilot test on a small sample of studies helps identify missing fields or ambiguous items before you extract data from all included studies. ### Data Items List the specific data items you will extract from each study. These should map directly to your research question and objectives. Common data items in biology and environmental science scoping reviews include: - Author and year - Study location and setting - Study design - Sample size or study scale - Species or system studied - Intervention or exposure - Outcome measures - Key findings ### Synthesis and Presentation of Results Describe how you will collate and present the findings. Scoping reviews typically present results in tables, charts, and narrative summaries. Specify the types of tables or figures you plan to produce and how you will organize the narrative synthesis. If you plan to group studies by theme, intervention type, or geographic region, describe that grouping here. ## Practical Workflow for Writing the Protocol ### Step 1: Draft the Research Question Begin with a broad topic and refine it through discussion with your team or supervisor. Write the question in PCC format and test it against a few known studies to confirm that it captures the literature you expect to find. ### Step 2: Develop and Test the Search Strategy Work with a librarian or information specialist to develop a search strategy for your primary database. Run the search, review a sample of results, and refine the terms. Document each iteration so you can describe the development process in the protocol. ### Step 3: Draft Each Protocol Section Write the protocol sections in the order presented above. Do not worry about perfect wording in the first draft. Focus on capturing the decisions you have made and the rationale for each decision. ### Step 4: Pilot the Eligibility Criteria and Data Charting Form Apply your eligibility criteria to a sample of 20 to 30 records and extract data from 5 to 10 included studies using your draft charting form. Revise the criteria and the form based on what you learn. ### Step 5: Circulate for Feedback Share the draft protocol with your co-authors, supervisor, or colleagues. Ask them to check for internal consistency, feasibility, and clarity. Revise accordingly. ### Step 6: Finalize and Register Finalize the protocol and consider registering it on a platform such as the Open Science Framework or a registry that accepts scoping review protocols. Registration creates a public record of your planned methods. ## Records and Measurements The protocol itself is a record, but you will also need to maintain several supporting documents throughout the review process. These include: | Supporting Document | Purpose | When to Update | | --- | --- | --- | | Search log | Records the date, database, and search string for every search run | After each search | | Screening log | Tracks the number of records screened, excluded, and included at each stage | After each screening session | | Data charting form | The standardized form used to extract data from included studies | After pilot testing and after any revisions | | Amendment log | Documents any changes to the protocol and the rationale for each change | Whenever a change is made | | PRISMA-ScR checklist | Tracks completion of each reporting item for the final review | Throughout the review process | The [NIH Data Management and Sharing Policy](https://sharing.nih.gov/data-management-and-sharing-policy) describes expectations for managing and sharing research data. While this policy applies to NIH-funded research, the underlying principle of documenting and preserving research records applies to any rigorous scoping review. Your search logs, screening decisions, and charting forms are data that should be preserved and made available to readers upon request. ## Common Failure Patterns in Protocol Writing ### Vague Eligibility Criteria The most common failure is writing eligibility criteria that cannot be applied consistently. For example, "studies on habitat fragmentation" is too vague. Does this include modeling studies? Does it include studies that measure fragmentation indirectly? Does it include studies of any organism or only vertebrates? Rewrite the criterion to specify the study designs, populations, and outcomes that will be included. ### Overly Broad Search Strategy A search strategy that returns tens of thousands of records may be comprehensive, but it may also be impractical to screen. If your search returns an unmanageable number of records, refine your terms or add filters before finalizing the protocol. Document the refinement process so readers understand how the final strategy was developed. ### Insufficient Duplicate Screening Screening all records with a single reviewer increases the risk of missing relevant studies. If you cannot screen in duplicate, document this limitation in the protocol and describe any quality-control measures you will use, such as having a second reviewer screen a random sample of excluded records. ### Undefined Data Charting Form A protocol that says "we will extract relevant data" without specifying the data items is not actionable. List the specific fields on your charting form and pilot-test the form before the protocol is finalized. ### No Plan for Handling Deviations Every scoping review deviates from its protocol to some degree. The protocol should specify how deviations will be documented and reported. A simple approach is to maintain an amendment log and to describe all deviations in the final review report. ## Limitations and Boundaries A protocol cannot anticipate every decision you will make during the review. Scoping reviews are iterative, and you will likely refine your search terms, eligibility criteria, or charting form as you become more familiar with the literature. The protocol should acknowledge this possibility and specify how you will document changes. The protocol also cannot guarantee the quality of the included studies. Scoping reviews map the literature instead of assess the risk of bias in individual studies. If your review aims to inform policy or practice decisions, you may need to consider whether a systematic review with quality assessment is more appropriate than a scoping review. Finally, a protocol is only as good as its execution. A well-written protocol that is not followed, or that is followed without documentation of deviations, provides little protection against bias. The discipline of maintaining search logs, screening logs, and amendment records is as important as the protocol document itself. ## Safety and Regulatory Context Scoping reviews in biology and environmental science may involve topics with regulatory implications, such as pesticide effects, endangered species, or water quality standards. The protocol should acknowledge any relevant regulatory context and specify how the review will handle studies that report on regulated substances or activities. For researchers conducting reviews that may inform policy, the [NIH Grants and Funding](https://grants.nih.gov/) portal provides context on how funded research is reviewed and managed. While this does not directly govern scoping review conduct, it illustrates the expectation that research methods be transparent and reproducible. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) core practices address authorship, data integrity, and conflict-of-interest disclosure. These practices apply to scoping reviews as they do to any research publication. Ensure that all authors meet authorship criteria, that data are reported accurately, and that any conflicts of interest are disclosed in the protocol and the final report. ## Professional Escalation Criteria You should seek additional guidance or escalate concerns in the following situations: - Your search strategy returns results that are clearly irrelevant or that miss studies you know are important. Consult a librarian or information specialist before proceeding. - You cannot reach agreement on eligibility criteria or data items among your review team. Involve a third reviewer or a methodologist to help resolve the disagreement. - You discover that a key database is not accessible through your institution. Document this limitation and consider whether alternative sources can fill the gap. - Your screening process reveals that your research question is not answerable with the available literature. Consult your supervisor or team to decide whether to revise the question or narrow the scope. - You are uncertain whether your review requires ethics approval. Check with your institutional review board or research ethics office before beginning data collection. ## Frequently Asked Questions ### What is the difference between a scoping review protocol and a systematic review protocol? A scoping review protocol maps the breadth of literature on a topic, while a systematic review protocol focuses on answering a specific question through rigorous synthesis of eligible studies. Scoping review protocols typically use the PCC framework for the research question, while systematic reviews often use PICO or a similar framework that includes intervention and comparison elements. The [EQUATOR Network](https://www.equator-network.org/) provides reporting guidelines for both study types, with PRISMA-ScR for scoping reviews and PRISMA for systematic reviews. ### Do I need to register my scoping review protocol? Registration is not mandatory for scoping reviews, but it is recommended. Registration creates a public record of your planned methods and helps prevent selective reporting. You can register on the Open Science Framework or other platforms that accept scoping review protocols. The protocol should state whether registration was completed and provide the registration number if applicable. ### How detailed should my search strategy be in the protocol? The search strategy should be detailed enough that another researcher could reproduce it. Include the full search string for at least one major database, the list of search terms and variants, any filters or limits, and the date range. If you refined the strategy during development, document the iterations so readers can see how the final version was derived. ### Can I change my protocol after it is written? Yes, but you must document the changes. Maintain an amendment log that records the date, the nature of the change, and the rationale. Report all deviations from the protocol in the final review report. The [Committee on Publication Ethics](https://publicationethics.org/core-practices) core practices emphasize transparent reporting, which includes disclosing changes to planned methods. ### How many reviewers do I need for screening and data charting? The protocol should specify the number of reviewers and the process for resolving disagreements. A common approach is to have two reviewers screen titles and abstracts independently, resolve disagreements by discussion or a third reviewer, and then screen full texts using the same process. Data charting is often done by one reviewer with verification by a second reviewer. If you use a single reviewer for any step, document this limitation in the protocol. ### What is a data charting form and how do I develop one? A data charting form is a standardized template used to extract information from each included study. It typically includes fields for bibliographic information, study characteristics, and findings relevant to your research question. Develop the form by listing the data items that map to your research question and objectives, then pilot-test the form on a small sample of studies to identify missing or ambiguous fields. ### How do I handle gray literature in a scoping review? Gray literature includes reports, theses, conference proceedings, and other materials not published in traditional journals. If you plan to include gray literature, specify the sources you will search and the criteria for inclusion. Gray literature can be valuable for scoping reviews because it often contains information not available in peer-reviewed publications, but it may also be more difficult to locate and assess. ### What should I do if my search returns too many or too few records? If your search returns too many records, refine your search terms, add filters, or narrow your eligibility criteria. If it returns too few, expand your search terms, add databases, or broaden your criteria. Document any changes to the search strategy or eligibility criteria in the protocol and the amendment log. Consult a librarian or information specialist if you are uncertain how to proceed. ## Related Articles - [What Is Data Management? A Primer for Life Science Researchers](/blog/guides/what-is-data-management-a-primer-for-life-science-researchers) - [Conducting Qualitative Interviews: A Guide for Life Science Researchers](/blog/guides/conducting-qualitative-interviews-a-guide-for-life-science-researchers) - [Conducting a Study: A Practical Checklist for Life Science Researchers](/blog/guides/conducting-a-study-a-practical-checklist-for-life-science-researchers) - [Observational vs. Experimental Studies: A Decision Framework for Life Science Researchers](/blog/guides/observational-vs-experimental-studies-a-decision-framework-for-life-science-researchers) - [Open Science Practices: A Guide for Researchers](/blog/guides/open-science-practices-a-guide-for-researchers) ## References and Further Reading - [Research Methods Resources](https://www.ncbi.nlm.nih.gov/books). National Library of Medicine. - [EQUATOR Network](https://www.equator-network.org/). EQUATOR Network. - [Core Practices](https://publicationethics.org/core-practices). Committee on Publication Ethics. - [NIH Grants and Funding](https://grants.nih.gov/). National Institutes of Health. - [ORCID for Researchers](https://info.orcid.org/researchers). ORCID. - [Data Management and Sharing Policy](https://sharing.nih.gov/data-management-and-sharing-policy). National Institutes of Health. - [NCBI Literature Resources](https://www.ncbi.nlm.nih.gov/). National Center for Biotechnology Information. - [PubMed](https://pubmed.ncbi.nlm.nih.gov/). National Library of Medicine. > This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.