PRISMA-S

What it is

PRISMA-S (PRISMA Extension for Reporting Literature Searches) is a 16-item reporting checklist that extends the parent PRISMA 2020 statement to cover one thing in depth: the search underlying a systematic review. It was developed by an international working group of information specialists and methodologists (Rethlefsen et al., 2021) under the EQUATOR Network umbrella and is maintained alongside the other PRISMA products at the PRISMA Statement website. Its sole purpose is search transparency and reproducibility — making the methods used to find studies explicit enough that a knowledgeable reader could appraise the search's adequacy and, in principle, reproduce it. PRISMA-S is a content extension, not a standalone guideline: it expands the search-related PRISMA 2020 items into granular, operational reporting requirements. It is deliberately narrow. It says nothing about study design, risk of bias, effect estimation, or synthesis methods.

When to use

Use PRISMA-S whenever a manuscript, protocol, or dossier reports a systematic search of the literature — systematic reviews, meta-analyses (of RCTs or observational studies), network meta-analyses, scoping reviews, rapid reviews, and the search sections of HTA submissions and guideline evidence reviews. PRISMA-S is applied in addition to the relevant PRISMA reporting set, not instead of it. Decision rule: report against PRISMA 2020 for the review as a whole, then layer PRISMA-S over the search to satisfy the search-reporting items at full granularity; if the review is a scoping review use PRISMA-ScR for the body and still layer PRISMA-S over its search, and likewise for PRISMA-IPD or PRISMA-NMA. PRISMA-S governs reporting at write-up and peer-review time; for conducting and peer-reviewing the search itself the methodological partner is PRESS (Peer Review of Electronic Search Strategies).

What it requires

PRISMA-S enforces complete, rerunnable documentation across the search lifecycle. Its item groups require: (1) Information sources — every database (with platform/vendor, e.g., MEDLINE via Ovid vs PubMed), trial registry, grey-literature source, web search engine, and the dates each was searched, plus any limits or coverage caveats. (2) Search strategies — the full, line-by-line search string for at least one database reproduced verbatim (not a paraphrase), and ideally for every source, including all controlled-vocabulary terms, free-text terms, field tags, Boolean operators, truncation, and the use of any published or methodological search filters (with their source). (3) Supplementary search methods — citation chasing (forward and backward), contacting authors or manufacturers, examining reference lists, and any hand-searching. (4) Search management and processing — the software or platform used to run/export searches, the deduplication method and tool, and total records before and after dedup. (5) Search peer review — whether the search strategy was peer reviewed (e.g., using PRESS) and by whom. The unifying standard is reproducibility: a reader should be able to reconstruct the search from the report alone.

When NOT to use — limitations and common misapplications

PRISMA-S is a reporting checklist, not a risk-of-bias instrument, not a quality score, and not a measure of search adequacy — checking every item only confirms that the search was described transparently, not that it was sensitive, unbiased, or appropriately scoped (that judgment needs PRESS and methodological appraisal). Common failures: (a) paraphrasing instead of pasting the actual search string, which defeats reproducibility — PRISMA-S requires the verbatim strategy, usually as a supplementary appendix; (b) reporting "PubMed, Embase, Cochrane" with no platform, no dates, and no strings (item-level non-compliance dressed up as compliance); (c) checklist-as-theater — ticking boxes and citing PRISMA-S while the search section remains irreproducible; (d) using PRISMA-S where a different PRISMA product governs the review type, or omitting the parent PRISMA 2020 set and treating PRISMA-S as if it covered the whole review (it does not — it covers only the search); (e) treating PRISMA-S compliance as evidence the review's conclusions are sound. PRISMA-S is also not a search-conduct guide: it tells you what to report, not how to design a sensitive strategy.

How it maps to this catalog

PRISMA-S is an evidence-synthesis reporting tool, so it complements the synthesis designs in this repo rather than any causal-inference concept. It applies to systematic-review, meta-analysis-rct, meta-analysis-obs, network-meta-analysis, and scoping-review: each of these implements a search that PRISMA-S governs the reporting of, and ipd-meta-analysis when an IPD synthesis runs its own search. Pair it with picots-framework-rwe, which defines the Population/Intervention/Comparator/Outcome/Timing/Setting scope that the search strategy must operationalize and that PRISMA-S then asks you to report faithfully. There is intentionally no cross-reference to causal-design concepts (target-trial-emulation, propensity scores, phenotype algorithms, time-zero, estimands, attrition) — those govern how primary RWE studies are designed and have nothing to do with how a review's literature search is reported; bolting them on would be a category error.

Applied note for RWE evidence synthesis

When a systematic review or meta-analysis synthesizes real-world evidence — for example, an HTA submission summarizing observational comparative-effectiveness or burden-of-disease studies — the individual RWE studies are designed and appraised with the catalog's RWE concepts, but the search that found them is still reported under PRISMA-S. That means documenting database platforms (and that registries such as ClinicalTrials.gov or EU PAS were searched for RWE/PASS studies), the verbatim strategies including any observational/RWE study-design filters, grey-literature and conference-abstract sources (often decisive for unpublished RWE), the dedup workflow, and whether the strategy was PRESS-reviewed. Keep this distinct from how the underlying RWE studies handled confounding, time-zero, or attrition — PRISMA-S has no opinion on those, and conflating the two is the most common scoping error.