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PRESS (Peer Review of Electronic Search Strategies) is a structured checklist used to have a second, independent information specialist or librarian review a systematic review’s search strategy before it is run for the final review — catching errors in logic, vocabulary, or scope while they are still cheap to fix. The current version, the PRESS 2015 Guideline Statement, was developed by Jessie McGowan, Margaret Sampson, Douglas M. Salzwedel, Elise Cogo, Vicki Foerster and Carol Lefebvre, building on an original 2008 PRESS project, and published in the Journal of Clinical Epidemiology in 2016. It was developed with support from what was then the Canadian Agency for Drugs and Technologies in Health (CADTH) — now Canada’s Drug Agency (CDA-AMC) — which continues to host the checklist as a free, publicly available tool.
Last verified 2026-08-31 against CASRAI’s existing citation practice for this literature; the primary CADTH/CDA-AMC page and the 2016 journal article were not independently re-fetched this session (both returned bot-verification/403 responses), so treat exact page numbers as REPORTED rather than freshly confirmed — the author list, journal, year, and six-element structure below are well-established, widely cited facts in the systematic-review methods literature.
What a PRESS Review Actually Checks
A PRESS review is not a re-run of the search itself. It is a peer reviewer — ideally a second, independent searcher — reading the strategy line by line before it is executed, the same way a statistical reviewer checks an analysis plan before the data are pulled. The goal is to catch a missed synonym, a broken Boolean nest, or a subject heading that no longer matches the current thesaurus while it still costs nothing to fix, rather than after thousands of records have already been screened.
The Six PRESS Elements
The 2015 Guideline Statement organizes the review around six elements. A reviewer works through each one against the strategy as drafted:
- Translation of the research question. Does the strategy’s set of concepts actually match the review’s PICO (or comparable) question, or has something been dropped, merged, or over-narrowed in translation?
- Boolean and proximity operators. Are AND/OR/NOT nested correctly, and do proximity operators (ADJ, NEAR, and similar) do what the searcher intended? A misplaced parenthesis is one of the most common ways a strategy silently drops relevant records.
- Subject headings. Are the correct controlled-vocabulary terms used for the database in question — MeSH in MEDLINE, Emtree in Embase — including current entry terms, and are they exploded or not exploded appropriately?
- Text word searching. Does the free-text component cover realistic spelling variants, synonyms, acronyms, and truncation, so the search doesn’t rely on subject headings alone (which can lag newly indexed literature)?
- Spelling, syntax, and line numbers. Line-by-line mechanical checks — a misspelled term, a syntax error specific to the database’s search interface, or a line-number reference that no longer points to the field it should.
- Limits and filters. Are date, language, publication-type, or species limits applied correctly and justified, rather than silently narrowing the results beyond what the protocol intended?
PRESS vs. PRISMA-S: Two Different Jobs
PRESS and PRISMA-S are easy to conflate because both concern the search, but they check different things at different points in the process. PRESS is a quality-improvement checklist, applied to the strategy before it is run, with a named peer reviewer signing off on it. PRISMA-S is a reporting checklist, applied after the search is complete, to make sure the final manuscript documents every database, platform, date range, and the complete executable strategy for each. A well-run review typically uses both: PRESS to improve the strategy in draft, PRISMA-S to report it faithfully once the review is finished. Neither substitutes for the other.
The PRESS EBC: A Self-Assessment Companion
Alongside the peer-review checklist itself, the PRESS project also produces an Evidence-Based Checklist (PRESS EBC) intended for a searcher to self-assess their own strategy against the same six elements before ever sending it for external review. Used this way, PRESS becomes a two-stage quality gate: a self-check by the original searcher, then an independent review by a second information specialist, both against the same criteria.
Who Should Do the Review, and When
PRESS assumes the reviewer is a second person with real search expertise — commonly a librarian or information specialist not involved in drafting the original strategy — rather than a content expert reviewing for topical relevance. It belongs at protocol stage, after the strategy is drafted but before it is finalized and registered or run for the review’s final set of results. Running a PRESS review after the search has already been executed and records screened defeats the purpose: any fix at that point means re-running the search and re-screening, which is exactly the wasted effort an upfront peer review is meant to avoid.
Where PRESS Fits Alongside Other Systematic-Review Checklists
PRESS is one piece of a review’s overall quality infrastructure, not a replacement for the others. It sits alongside, but does not overlap with, tools like ROBIS (which assesses whether the finished review itself was conducted rigorously) and study-level risk-of-bias tools. A systematic reviewer translating a strategy across databases — for example following the workflow in CASRAI’s guide on translating a search from PubMed to Embase — is exactly the kind of task PRESS review is designed to sit downstream of, since translation errors are one of the most common findings a PRESS review surfaces. Comprehensive search coverage itself, including grey literature, is a related but separate concern from strategy quality within the databases actually searched.
Frequently Asked Questions
Is a PRESS review mandatory for a systematic review? No single body mandates it, but it is increasingly expected: some journals and funders ask authors to confirm a peer-reviewed search strategy, and Cochrane reviews are expected to have search strategies checked by a second information specialist, consistent with PRESS’s approach even where PRESS itself isn’t named as the exact instrument used.
Does PRESS apply to every database in a multi-database search? The checklist is applied per strategy, so a review searching MEDLINE, Embase, and CINAHL would ideally have each translated strategy reviewed, since subject headings and syntax differ by database and a translation error in one does not imply the others are also correct.
What’s the difference between the original 2008 PRESS project and the 2015 Guideline Statement? The 2008 version was the initial evidence-based checklist; the 2015 Guideline Statement is a revision developed through a formal consensus process among methodologists, refining the six elements above into the current standard framework, and it is the version now generally cited as “PRESS” without further qualification.
Who is qualified to conduct a PRESS review? The literature describes it as a task for a searcher with real database expertise — typically a health sciences librarian or information specialist — not simply a second author on the review team without dedicated search training.
See CASRAI’s Publishing & Research Assessment hub for related standards on how systematic reviews and their search strategies are reported, registered, and assessed.
