PRISMA-P (PRISMA for Protocols)

What it is

— PRISMA-P (Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols) is a 17-item reporting checklist that defines the minimum information a protocol for a systematic review or meta-analysis should report, so that the review's methods are pre-specified, transparent, and auditable before any study is screened or any effect is pooled. It was published as the 2015 statement (Moher, Shamseer et al.) with a companion explanation-and-elaboration paper (Shamseer et al.), and is hosted and maintained as a PRISMA extension within the EQUATOR Network. PRISMA-P is the protocol-stage member of the PRISMA family: it governs what you commit to in advance, whereas PRISMA 2020 governs how you report the completed review. Its purpose is to make the planned eligibility criteria, search strategy, risk-of-bias plan, outcomes, and synthesis approach explicit up front, so that deviations are visible and selective reporting and post-hoc data-dredging are constrained.

When to use

— Apply PRISMA-P whenever you are writing or registering the protocol for a systematic review or meta-analysis, including reviews of randomized trials, reviews of observational/real-world-evidence (RWE) studies, and mixed evidence. It is the appropriate checklist for a PROSPERO registration record, a protocol manuscript (e.g., Systematic Reviews, BMJ Open), and the evidence-synthesis protocol underpinning an HTA/payer dossier or a regulatory evidence package that relies on a systematic review. Decision rule for choosing the right family member: use PRISMA-P for the plan; use PRISMA 2020 for the finished review report; if the review is a scoping review use PRISMA-ScR; if it is a network meta-analysis use the PRISMA-NMA extension for the report. PRISMA-P governs the protocol regardless of which downstream PRISMA extension reports the results. It does not govern primary study protocols — a single observational cohort/case-control RWE study uses HARPER, the ENCePP checklist, or SPIRIT (for trials), not PRISMA-P.

What it requires

— The 17 items (organized as administrative information, introduction, and methods) compel pre-specification of the elements that otherwise drift during a review: title/registration; protocol amendments and version control; rationale and objectives framed as a structured PICOTS question (population, interventions/exposures, comparators, outcomes, timing, setting/study designs); explicit eligibility criteria including study designs admitted; a reproducible information-sources and search strategy (named databases, draft search string for at least one database, planned date ranges); a study-selection and data-extraction process (screening, duplication, calibration); a pre-specified list of outcomes and other variables; a planned risk-of-bias / quality-assessment approach for the included studies (the tool to be used and the level at which it is applied); and the planned data synthesis (effect measures, handling of heterogeneity, quantitative pooling vs narrative, planned subgroup/sensitivity analyses, and assessment of meta-bias such as publication bias and selective outcome reporting). For an RWE-heavy review these generic items carry specific weight: the eligibility criteria must state which real-world data designs and data sources are admissible; the risk-of-bias plan must name an instrument suited to non-randomized studies (e.g., ROBINS-I) and, where outcomes are algorithm-defined, the protocol should pre-specify how it will appraise phenotype/outcome algorithm validity, time-zero alignment, and confounding control across the included studies; and the synthesis section must pre-commit to whether heterogeneous observational estimands are poolable at all or only qualitatively synthesized.

When NOT to use — limitations and common misapplications

— PRISMA-P is a reporting checklist for a protocol; it is not a quality score, not a risk-of-bias instrument, and not a guarantee of a valid review. Concrete failure modes: (1) Wrong family member — using PRISMA-P to report the completed review (use PRISMA 2020) or, conversely, citing PRISMA 2020 for a protocol. (2) Wrong checklist entirely — applying PRISMA-P to a primary observational/RWE study protocol; a single claims/EHR cohort study should follow HARPER, the ENCePP checklist, or STROBE/RECORD-PE for reporting, never PRISMA-P. (3) Mistaking it for an appraisal tool — PRISMA-P says nothing about whether the included studies are sound; the included studies are appraised with ROBINS-I/ROB 2 and the review's own conduct with AMSTAR 2. (4) PROSPERO ≠ compliance — registering a record is not the same as completing the checklist; do both, and keep the registration synchronized with protocol amendments. (5) Checklist-as-theater — ticking 17 boxes while leaving eligibility criteria, the search string, the risk-of-bias plan, or the synthesis method vague defeats the purpose; the value is the pre-specification, not the page count. (6) Completing the checklist does not make a pooled observational estimate causal or unconfounded — a fully PRISMA-P-compliant protocol can still plan a meta-analysis of biased studies; transparency of the plan is necessary, not sufficient.

How it maps to this catalog

— In this repo, PRISMA-P's requirements are implemented by concepts a reviewer can pre-specify against: - The review object and synthesis machinery: systematic-review, meta-analysis-obs, meta-analysis-rct (and, for the report stage, network-meta-analysis). - The structured question / eligibility spine (PRISMA-P items 8–10): picots-framework-rwe operationalizes the population/intervention/comparator/outcome/timing/setting frame the protocol must declare. - The protocol-content discipline itself: study-protocol-or-sap-elements supplies the pre-specification and amendment-control habits PRISMA-P's administrative and methods items demand. - Appraisal of the included RWE studies (planned in the risk-of-bias item, not implemented by PRISMA-P itself): when the review pools real-world studies, the protocol should commit to appraising them against algorithm-validation (outcome/phenotype algorithm validity), generalizability-transportability-external-validity-rwe, and the design-validity concepts those primary studies rely on — target-trial-emulation, active-comparator-new-user, estimands-ate-att-intercurrent-events-rwe, diagnosis-phenotype-algorithm-1ip-2op-time-window-rwe, attrition-and-loss-to-follow-up-rwe, and high-dimensional-propensity-score-hdps-rwe. These are not PRISMA-P items for the protocol's own conduct; they are the lens the protocol pre-specifies for grading the evidence it will synthesize.

Applied note (claims/EHR/registry RWE)

A systematic review pooling claims- and EHR-based comparative studies should, at the protocol stage, state which data designs are admissible (e.g., active-comparator new-user cohorts vs prevalent-user designs), pre-specify a non-randomized risk-of-bias instrument and how time-zero, confounding, and algorithm-defined outcomes will be judged across heterogeneous data sources, and decide in advance whether estimates from different databases and estimands are quantitatively poolable or only narratively synthesized — the questions PRISMA-P items on eligibility, risk of bias, and synthesis exist to force.