Systematic Review ProtocolEdit

A systematic review protocol is the preplanned blueprint for conducting a systematic review of the literature. It specifies the research question, eligibility criteria, search strategy, study selection process, data extraction methods, risk of bias assessment, and planned analyses. By laying out these elements in advance, the protocol helps ensure that the eventual review is transparent, reproducible, and less prone to subjective influence.

Protocols are used across disciplines, from medicine and public health to education and social sciences. They function as a contract between researchers and readers: a clear statement of what will be done, how it will be done, and what kinds of evidence will count toward conclusions. When protocols are registered or published, they create accountability and enable others to scrutinize planned methods before results are known. See also Systematic review and evidence synthesis for related concepts.

Purpose and value

  • Transparency and accountability: A protocol documents the exact questions and methods, making deviations visible if they occur later. This supports trust in the review process and its conclusions.
  • Reproducibility and updating: With a detailed plan, other researchers can replicate the work or update it when new evidence emerges. See protocol and systematic review for related ideas.
  • Bias reduction: Predefining inclusion criteria, outcomes, and analysis plans reduces opportunities for post hoc changes that could tilt findings.
  • Quality and comparability: Protocols provide a standard against which final reviews can be judged, aiding comparisons across studies and disciplines. See risk of bias and GRADE for methods used to assess evidence quality.

Key elements of a Systematic Review Protocol

  • Research question and objectives: A focused question guides the scope and determines which studies will be relevant. Often formatted using a framework such as PICOS (participants, interventions, comparators, outcomes, study design).
  • Eligibility criteria: Predefined criteria for including or excluding studies, including population characteristics, intervention types, outcomes of interest, and study designs.
  • Information sources and search strategy: The databases, journals, gray literature sources, and search terms used to locate studies. A transparent search strategy enables replication; see search strategy.
  • Study selection process: How studies will be screened (usually in stages, e.g., title/abstract screening followed by full-text review) and who will perform these steps.
  • Data extraction and management: Tools and procedures for pulling out relevant information (e.g., study design, population, interventions, outcomes, results) and resolving disagreements.
  • Risk of bias assessment: Methods for evaluating the internal validity of included studies, such as checklists or domain-based approaches.
  • Data synthesis plan: How evidence will be combined, including options for narrative synthesis and quantitative methods like meta-analysis (see meta-analysis).
  • Subgroup and sensitivity analyses: Plans for exploring heterogeneity and testing robustness of findings.
  • Certainty of evidence: Approaches to rate confidence in the results, such as the GRADE framework.
  • Publication bias and reporting: Strategies to address potential biases in published literature and how results will be disseminated, including adherence to reporting standards like PRISMA-P and PRISMA.
  • Amendments and versioning: How changes to the protocol will be recorded and communicated to readers.
  • Ethics and dissemination: Considerations related to ethical approval (if applicable) and plans for sharing results with stakeholders.

Protocol development and publication

  • Development process: Teams draft the protocol before initiating the review, often involving stakeholders who can provide methodological expertise or subject-matter insights.
  • Registration and preregistration: Public registries such as PROSPERO host protocols so researchers and readers can compare planned methods with what is reported in the final review. In medicine and related fields, preregistration is widely encouraged as a best practice.
  • Publication: The protocol itself may be published as a separate article or indexed within a broader study protocol collection. Publication enhances visibility and invites scrutiny that can improve the final review.

Standards, reporting, and reproducibility

  • PRISMA-P and related guidelines: Protocol reporting standards help ensure completeness and consistency in what is documented. See PRISMA-P and PRISMA for the broader family of reporting guidelines.
  • Data and materials sharing: Authors may provide access to data extraction forms, instructions, and analytic code to facilitate replication, re-use, and verification.
  • Living and updateable protocols: Some reviews adopt a living approach, updating the protocol and review as new evidence becomes available. See living systematic review for related concepts.

Challenges and debates

  • Flexibility versus rigidity: A central debate concerns how strictly a protocol should constrain methods. Proponents of strict preregistration emphasize transparency; critics worry that overly rigid plans can hinder adaptation when new, important evidence emerges.
  • Exploratory analyses: While preregistration helps prevent bias, researchers sometimes discover unanticipated findings that warrant deviation from the original plan. Balancing confirmatory and exploratory analyses remains an ongoing methodological question.
  • Timeliness and resource demands: Developing a thorough protocol requires time and expertise, which can slow evidence generation in fast-moving fields. Some researchers advocate streamlined or modular protocols to mitigate this issue.
  • Generalizability across fields: Different disciplines have varying norms around study design and reporting, which can complicate the creation of universally applicable protocol standards.

Applications and impact

  • In healthcare, systematic review protocols underpin evidence syntheses that inform guidelines and clinical decision-making. See systematic review and meta-analysis for how protocol-driven reviews contribute to quantitative syntheses.
  • In policy and public health, transparent protocols support accountability when reviews influence regulatory or funding decisions. This is closely tied to the credibility of evidence synthesis as a basis for policy.
  • In education and social sciences, predefined protocols help manage complexity and reduce bias in reviews of interventions and outcomes.

See also