Scoping Review vs. Systematic Review: Key Differences and How to Choose

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-27

Quick Answer

• Choose a scoping review when your goal is to map the breadth of evidence on a broad topic, identify gaps, or clarify key concepts and definitions.
• Choose a systematic review when your goal is to answer a narrow, specific question by synthesizing all available evidence with rigorous, reproducible methods.
• A scoping review does not typically assess the quality of included studies or produce a pooled effect estimate, so it cannot answer questions about intervention effectiveness with the same certainty as a systematic review.

Understanding the Core Distinction

Researchers in the life sciences, animal health, and laboratory medicine frequently face a methodological fork in the road. The decision between a scoping review and a systematic review shapes every subsequent step of the research process, from protocol development to the final published output. Both approaches share a commitment to transparency and reproducibility, but they answer fundamentally different types of questions.

A systematic review is designed to answer a focused clinical or scientific question, typically about the effectiveness of an intervention, the accuracy of a diagnostic test, or the strength of an association. It uses exhaustive search strategies, explicit inclusion criteria, and rigorous quality appraisal to minimize bias. The output is often a quantitative synthesis, such as a meta-analysis, that provides a pooled estimate of effect across multiple studies.

A scoping review, by contrast, is designed to map the existing literature on a broader topic. It addresses questions such as "What types of evidence exist on this subject?" or "How has this concept been defined across different studies?" Scoping reviews do not typically assess the quality of included studies or synthesize findings quantitatively. Instead, they provide a structured overview of the volume, nature, and characteristics of the available evidence.

The choice between these two approaches is not a matter of preference. It is a decision driven by the research question, the state of the evidence base, and the intended use of the findings. Selecting the wrong approach can lead to wasted effort, misleading conclusions, or a manuscript that fails peer review.

At a Glance

When to Use a Scoping Review

Broad or Emerging Topics

A scoping review is the appropriate choice when the research question is broad, the topic is emerging, or the literature is heterogeneous in its methods and definitions. For example, a researcher investigating the various methods used to assess pain in laboratory animals across different species and experimental models would benefit from a scoping review. The goal is not to determine which method is most effective but to describe the range of methods, how they are applied, and where the gaps in validation lie.

Scoping reviews are also valuable when the body of literature has not yet been comprehensively reviewed. In rapidly evolving fields, such as the use of novel biomarkers in veterinary diagnostics, a scoping review can establish the current landscape before more focused systematic reviews are undertaken.

Concept Clarification and Definitional Work

When researchers need to understand how a concept has been defined, measured, or operationalized across different studies, a scoping review provides the structured approach needed. This is particularly relevant in fields where terminology is inconsistent. For instance, the term "welfare" in animal science has been defined in multiple ways across the literature. A scoping review can map these definitions, identify areas of consensus and disagreement, and provide a foundation for future standardization efforts.

Identifying Evidence Gaps

Scoping reviews are explicitly designed to identify gaps in the evidence base. The output often includes a clear articulation of what is known, what is not known, and where future research should focus. This makes scoping reviews valuable precursors to primary research studies or systematic reviews. Funding agencies, including the National Institutes of Health, expect applicants to demonstrate a clear understanding of the existing evidence landscape when proposing new research. A well-conducted scoping review provides exactly this foundation.

When a Systematic Review Is Premature

In some cases, a systematic review is not feasible because the evidence base is too sparse, too heterogeneous, or too poorly reported to support meaningful synthesis. Attempting a systematic review under these conditions can produce misleading results or a review that includes so few studies that the findings are uninformative. A scoping review allows researchers to document the state of the evidence honestly and to make the case for why primary research is needed.

When to Use a Systematic Review

Focused Questions About Effectiveness

The systematic review is the method of choice when the research question is narrow and specific, particularly when it concerns the effectiveness of an intervention. For example, a researcher asking whether a specific antibiotic protocol reduces the incidence of post-surgical infection in companion animals has a question that demands a systematic review. The review would identify all randomized controlled trials and quasi-experimental studies addressing this question, assess their quality, and synthesize their findings.

Informing Clinical or Policy Decisions

Systematic reviews are designed to inform decisions. Clinical practice guidelines, regulatory decisions, and institutional policies are built on the foundation of systematic reviews because they provide the most reliable summary of the evidence. When the findings of a systematic review will directly influence practice recommendations or resource allocation, the rigor of the systematic approach is essential.

Quantitative Synthesis Is Possible

When the included studies are sufficiently similar in their design, population, intervention, and outcome measures, a meta-analysis can be performed. This quantitative synthesis provides a pooled effect estimate with greater statistical power than any individual study. The decision to perform a meta-analysis is made after the systematic review process has identified and assessed the eligible studies.

Requirements From Journals and Funders

Many high-impact journals and funding agencies expect systematic reviews to follow established reporting guidelines and to be registered prospectively. The EQUATOR Network provides a comprehensive library of reporting guidelines, including PRISMA for systematic reviews and PRISMA-ScR for scoping reviews. Researchers should consult these guidelines early in the planning process to ensure their review will meet publication standards. The Committee on Publication Ethics Core Practices also emphasize the importance of transparent and complete reporting in all research outputs.

Practical Workflow for Making the Decision

Step 1: Define the Research Question

Write the research question in explicit terms. If the question can be structured using the PICO framework (Population, Intervention, Comparison, Outcome), a systematic review is likely appropriate. If the question is broader and exploratory, such as "What approaches have been used to study X?" or "What are the key concepts and definitions in this field?", a scoping review is the better fit.

Step 2: Assess the State of the Evidence

Conduct a preliminary search of the literature. If you find a large and heterogeneous body of work with inconsistent methods and definitions, a scoping review will help you map this landscape. If you find a focused body of studies that address a specific question with comparable methods, a systematic review is feasible and appropriate.

Step 3: Consider the Intended Output

Ask what the final product needs to accomplish. If the goal is to provide a pooled effect estimate or a detailed explanation to a clinical question, a systematic review is required. If the goal is to describe the state of the science, identify gaps, or clarify concepts, a scoping review will serve the purpose.

Step 4: Evaluate Available Resources

Systematic reviews require substantial time, expertise, and resources. They demand comprehensive searching, duplicate screening, quality appraisal, and often statistical expertise for meta-analysis. Scoping reviews are less resource-intensive but still require rigorous methods and transparent reporting. Be honest about what you can deliver within your constraints.

Step 5: Consult Reporting Guidelines

Before finalizing your decision, consult the EQUATOR Network to identify the appropriate reporting guideline for your chosen approach. For systematic reviews, PRISMA is the standard. For scoping reviews, PRISMA-ScR provides the framework. Following these guidelines from the outset will improve the quality of your review and its chances of successful publication.

Decision Flowchart

flowchart TD
    A[Define your research question] --> B{Is the question narrow and specific?}
    B -->|Yes| C{Does it address intervention effectiveness or a precise association?}
    C -->|Yes| D[Systematic Review]
    C -->|No| E{Is the goal to map evidence or clarify concepts?}
    B -->|No| E
    E -->|Yes| F[Scoping Review]
    E -->|No| G[Consider other review types]
    D --> H[Assess feasibility: sufficient comparable studies?]
    H -->|Yes| I[Proceed with systematic review and meta-analysis if appropriate]
    H -->|No| F

Methodological Differences in Practice

Search Strategy Development

The search strategy for a systematic review is comprehensive and designed to capture all relevant studies, including those in gray literature and non-English sources. The search is documented in full detail so that it can be reproduced. For a scoping review, the search is often iterative. Initial searches inform subsequent refinements as the reviewer becomes more familiar with the terminology and key concepts in the field.

Study Selection and Screening

Both approaches use explicit inclusion and exclusion criteria, and both require that screening decisions be made independently by at least two reviewers to reduce bias. The difference lies in the nature of the criteria. Systematic reviews use criteria that are tightly aligned with the PICO framework. Scoping reviews use broader criteria that capture the range of study designs, populations, and outcomes relevant to the mapping exercise.

Data Extraction

In a systematic review, data extraction is focused on the specific variables needed for synthesis, such as effect sizes, sample sizes, and study characteristics. In a scoping review, data extraction is broader and captures the range of information needed to describe the evidence landscape, including study designs, geographic locations, populations, and key findings.

Quality Appraisal

Quality appraisal is a defining difference between the two approaches. Systematic reviews require a rigorous assessment of the risk of bias in each included study. This appraisal informs the synthesis and the certainty of the conclusions. Scoping reviews typically do not include quality appraisal as a formal step. When quality is considered, it is described narratively instead of used to exclude studies or weight their contributions.

Synthesis and Presentation

Systematic reviews synthesize findings quantitatively when possible, producing pooled effect estimates with confidence intervals. When meta-analysis is not appropriate, systematic reviews use structured narrative synthesis. Scoping reviews present findings as a map of the evidence, often using tables, charts, and narrative descriptions to show the volume, distribution, and characteristics of the literature.

Records and Documentation

Protocol Development

Both review types benefit from a protocol that is developed before the review begins. The protocol should specify the research question, search strategy, inclusion criteria, data extraction approach, and synthesis methods. For systematic reviews, protocol registration in a repository such as PROSPERO is expected by many journals and funders. Scoping review protocols can also be registered, and this practice is increasingly recommended.

Search Documentation

Maintain a complete record of all searches, including databases searched, dates, search strings, and numbers of records retrieved. This documentation is essential for reproducibility and is required by reporting guidelines. The National Library of Medicine provides access to authoritative biomedical books and research-method references that can guide the development and documentation of search strategies.

Screening Records

Track the number of records identified, screened, assessed for eligibility, and included in the final review. This information is presented in a flow diagram, which is a required element of both PRISMA and PRISMA-ScR reporting.

Data Management

Plan for data management from the outset. The National Institutes of Health Data Management and Sharing Policy outlines expectations for the management and sharing of research data. While this policy applies to NIH-funded research, the principles of good data management apply to all research. Store screening decisions, extraction forms, and analysis files in a structured and accessible format.

Common Failure Patterns

Choosing the Wrong Review Type

The most common failure is selecting a scoping review when a systematic review is needed, or vice versa. This error typically stems from an unclear research question. If the question is about effectiveness, a scoping review will not provide the answer. If the question is about mapping the evidence landscape, a systematic review will be unnecessarily restrictive and may exclude relevant studies.

Incomplete or Biased Searching

A systematic review that fails to search all relevant databases, omits gray literature, or applies language restrictions without justification will miss relevant studies and introduce bias. A scoping review that relies on a single database or an unstructured search will produce an incomplete map of the evidence.

Inadequate Duplicate Screening

Both review types require independent screening by at least two reviewers. Failing to implement this process, or resolving disagreements without a clear procedure, undermines the reliability of the review.

Ignoring Reporting Guidelines

Submitting a review that does not follow the relevant reporting guideline is a common cause of rejection or revision requests. The EQUATOR Network provides the tools to identify and follow the correct guideline from the start.

Overstating Conclusions

A scoping review cannot support conclusions about intervention effectiveness. Claiming that a scoping review demonstrates the superiority of one approach over another is a fundamental error. Similarly, a systematic review with a small number of low-quality studies cannot support strong recommendations.

Quality and Transparency Considerations

Reporting Guidelines

The EQUATOR Network is the primary resource for identifying reporting guidelines. For systematic reviews, PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) is the standard. For scoping reviews, PRISMA-ScR provides the specific reporting requirements. These guidelines ensure that reviews are reported completely and transparently, allowing readers to assess the methods and the validity of the conclusions.

Publication Ethics

The Committee on Publication Ethics Core Practices address fundamental issues in research publication, including authorship, peer review, data access, and conflicts of interest. These practices apply to review articles as much as to primary research. Ensure that all authors meet the criteria for authorship, that the review is original, and that any conflicts of interest are declared.

Researcher Identity and Attribution

Maintaining an accurate researcher record is important for the recognition of your work. ORCID provides a persistent digital identifier that distinguishes you from other researchers and ensures that your publications are correctly attributed to you. Linking your ORCID to your review articles and other outputs helps build your research profile and facilitates proper citation.

Welfare and Safety Context

Animal Research Reviews

When conducting reviews in animal research, the welfare of the animals in the included studies is a relevant consideration. A systematic review of interventions that affect animal welfare should assess also the effectiveness of the interventions but also any welfare implications reported in the included studies. A scoping review can map the range of welfare indicators used across studies, identifying gaps in the measurement and reporting of welfare outcomes.

Laboratory Safety

Reviews that address laboratory procedures or occupational exposures should consider safety outcomes as part of the synthesis. Systematic reviews of interventions to reduce laboratory-acquired infections, for example, would include safety outcomes as primary or secondary endpoints. Scoping reviews can map the types of safety data reported in the literature, highlighting areas where reporting is inadequate.

Responsible Conduct of Research

The conduct of any review, whether scoping or systematic, should adhere to the principles of responsible research conduct. This includes transparency in methods, accuracy in reporting, and honesty in the interpretation of findings. The National Institutes of Health provides guidance on the responsible conduct of research through its grants and funding resources, and researchers should be familiar with these expectations.

Professional Escalation Criteria

When to Seek Expert Guidance

If you are uncertain about the appropriate review type after working through the decision process, consult a librarian with expertise in systematic review methods or a statistician with experience in evidence synthesis. These professionals can help you refine your research question and determine the most appropriate approach.

When to Revise Your Approach

If your preliminary searches reveal that the evidence base is substantially different from what you expected, be prepared to revise your approach. A planned systematic review may need to become a scoping review if the evidence is too sparse or heterogeneous. A planned scoping review may need to become a systematic review if you discover a focused body of high-quality studies that can support synthesis.

When to Stop and Reassess

If you find that your research question cannot be answered by either approach, stop and reassess. The question may need to be reframed, or a different type of review, such as a narrative review or a rapid review, may be more appropriate. Continuing with an inappropriate method will produce a review that fails to meet its objectives.

Frequently Asked Questions

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

The main difference lies in the purpose. A scoping review maps the breadth and nature of evidence on a broad topic, identifying gaps and clarifying concepts. A systematic review answers a focused question by synthesizing all relevant evidence with rigorous methods, often producing a pooled effect estimate.

Can a scoping review include a quality assessment of the included studies?

Scoping reviews typically do not include formal quality assessment. When quality is considered, it is described narratively instead of used to exclude studies or weight their contributions. Systematic reviews, by contrast, require rigorous risk-of-bias assessment as a core component of the method.

How long does a systematic review take compared with a scoping review?

Systematic reviews generally take substantially longer, often 12 to 24 months from protocol to publication. Scoping reviews are typically less resource-intensive but still require rigorous methods and can take 6 to 12 months. The exact timeline depends on the scope of the question, the volume of literature, and the size of the review team.

Do I need to register my review protocol?

Protocol registration is expected for systematic reviews and is required by many journals and funders. Registration in a repository such as PROSPERO provides transparency and reduces the risk of duplication. Scoping review protocols can also be registered, and this practice is increasingly recommended.

What reporting guidelines should I follow?

The EQUATOR Network provides the definitive library of reporting guidelines. For systematic reviews, follow PRISMA. For scoping reviews, follow PRISMA-ScR. Consult the EQUATOR Network early in your planning process to ensure your review will meet reporting standards.

Can a scoping review be used to inform a systematic review?

Yes. A scoping review can serve as a precursor to a systematic review by mapping the evidence landscape, identifying the range of study designs and outcomes, and clarifying definitions. This preliminary work can inform the development of a more focused systematic review question and protocol.

What is the role of gray literature in these reviews?

Gray literature, including theses, conference abstracts, and government reports, can be important sources of evidence in both review types. Systematic reviews often include gray literature to reduce publication bias. Scoping reviews may include gray literature to capture the full range of evidence on a topic.

How do I choose between a scoping review and a systematic review for my thesis or dissertation?

Consider your research question, the state of the evidence, and the expectations of your program. If your question is broad and exploratory, a scoping review may be more appropriate. If your question is focused and you have the resources for a rigorous synthesis, a systematic review will provide a stronger contribution to the literature. Consult your supervisor and a librarian with expertise in evidence synthesis.

Using the Evidence

Related Articles

• Meta-Analysis Research Topics: How to Choose a Viable Question
• Meta-Analysis vs Scoping Review: Which Approach Answers Your Question?
• Cross-Sectional vs. Case-Control Studies: Key Differences and How to Choose
• Scoping Review vs Meta-Analysis: Clarifying Their Distinct Roles in Evidence Synthesis
• Meta-Analysis vs Systematic Review: What's the Difference?

References and Further Reading

• Research Methods Resources. National Library of Medicine.
• EQUATOR Network. EQUATOR Network.
• Core Practices. Committee on Publication Ethics.
• NIH Grants and Funding. National Institutes of Health.
• ORCID for Researchers. ORCID.
• Data Management and Sharing Policy. National Institutes of Health.
• NCBI Literature Resources. National Center for Biotechnology Information.
• PubMed. National Library of Medicine.

This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.