What is PRESS in a systematic review?

PRESS stands for Peer Review of Electronic Search Strategies. It is a structured framework that guides an experienced second searcher through checking a draft search, covering question translation, Boolean and proximity logic, subject headings, spelling, and syntax before the search is run in full.

Why should a search strategy be peer reviewed?

Search errors such as a missing synonym or misplaced operator silently drop eligible studies, and because the lost records never appear, the author cannot notice them. Peer review catches these invisible faults early, when they are far cheaper to fix than after screening and synthesis.

When should you peer review a search strategy?

Peer review is best done on the primary strategy before it is translated and run across other databases, so a corrected master strategy carries clean logic everywhere. For high-stakes reviews, some teams also peer review the translated versions.

Who should peer review a search strategy?

An experienced searcher or information specialist who was not involved in building the strategy should conduct the review. A fresh, expert pair of eyes is more likely to spot missing terms, logic errors, and syntax slips than the person who drafted the search.

What does the PRESS checklist actually check?

PRESS works through six recurring failure points: whether the search translates the question and matches the eligibility criteria, the Boolean and proximity logic, the subject headings, the free-text synonym lists, the spelling, truncation, and field tags, and any limits or filters. Each element maps to a concrete way a search can silently drop eligible studies.

Is search peer review required for publication?

It is not universally mandatory, but it is a recognised marker of a well-conducted search and is rewarded by appraisal tools such as AMSTAR 2. Many journals and guideline bodies expect it, and reporting that the strategy passed PRESS peer review strengthens the review against later scrutiny.

Peer Review of Search Strategies (PRESS)

Peer review of search strategies is a structured check in which a second, experienced searcher examines a draft search line by line before it is run in full. The most widely used framework is PRESS (Peer Review of Electronic Search Strategies), which guides the reviewer through the question translation, Boolean and proximity logic, subject headings, spelling and syntax, and any limits or filters, catching errors while they are still cheap to fix.

Why a search needs a second pair of eyes

A search strategy is intricate, and small mistakes have outsized consequences. A missing synonym, a misplaced operator, or a wrong field code can silently drop dozens of eligible studies, and because the lost records never appear, the author has no way of noticing. Peer review exists precisely because these failures are invisible from the inside. Catching them before the full search runs is far cheaper than discovering a gap after screening, extraction, and synthesis are already underway. It is the search-stage equivalent of the duplicate checks built into screening with two reviewers.

The PRESS checklist works through translation, Boolean logic, headings, and syntax before a search is run at scale.

What PRESS examines

Translation of the question

The reviewer first checks that the search actually reflects the review question. Every concept that should be searched is present, no concept that should have been left out, such as the outcome, has crept in, and the concept blocks match the eligibility criteria.

Boolean and proximity logic

Next the reviewer audits the combination logic: synonyms joined with OR, concept blocks joined with AND, and no ungrouped mixing of operators. Logic errors are among the most common and most damaging faults, which is why they get close attention. The mechanics behind this check are covered in Boolean operators for literature searching.

Subject headings and free-text

The reviewer confirms that relevant subject headings were used, exploded where appropriate, and paired with a full set of free-text synonyms. Missing headings or thin synonym lists are flagged as sensitivity risks.

Spelling, syntax, and line operations

Finally the reviewer checks spelling, truncation symbols, field tags, and how the lines are combined, since a single typo or wrong symbol can break a line without any error message. Database-specific syntax is checked again whenever a strategy is translated for another database, because translation introduces fresh chances for error.

When to run the peer review

Peer review works best on the primary strategy before it is translated and run everywhere, so a corrected master strategy carries clean logic into every other database. Some teams peer review again after translation for high-stakes reviews. Either way it is a planned step in the systematic search workflow, not an afterthought.

The six elements PRESS works through

The PRESS framework is built around a small set of recurring failure points, and running a draft against them in order turns a vague “does this look right” into a structured audit:

Translation of the question, confirming the concepts searched match the eligibility criteria and that the outcome was correctly left out.
Boolean and proximity operators, checking for the ungrouped AND-or-OR mixing that retrieves the wrong set.
Subject headings, confirming relevant headings were used and exploded where appropriate.
Free-text terms, checking the synonym lists are full rather than relying on one obvious word per concept.
Spelling, truncation, and field tags, where a single typo or wrong symbol can break a line with no error message.
Limits and filters, confirming any date, language, or design limit is validated and justified rather than silently trimming the result.

Each element maps to a concrete way a search can fail, which is what stops the review being a matter of taste. The reviewer is checking the strategy against the same eligibility rules the search is meant to operationalise.

A worked peer review catch

A concrete example shows why a second searcher is worth the time. Imagine a draft intervention block that lists the heading and the obvious free-text term but stops there. The peer reviewer pulls two studies the author knows are eligible, finds that one uses an abbreviation never added to the block and the other a spelling variant the truncation did not reach, and flags both as sensitivity gaps. Adding the abbreviation and widening the truncation recovers them. None of this was visible to the author, because the missing records simply never appeared, which is the recurring theme of why search errors are invisible from the inside and why an independent check of the search workflow is a planned step rather than an optional extra.

Recording the peer review

Note that a peer review took place, what the framework was, and what changed as a result, then carry that into documenting and reporting your search. Reporting that the strategy was peer reviewed is a recognised marker of a well-conducted search and strengthens the review against later scrutiny when it is appraised with a tool such as AMSTAR 2.

Common peer-review failures

The way teams use peer review can blunt it. The first failure is self-review, where the person who built the strategy checks their own work and reproduces their own blind spots; the reviewer should be someone who was not involved in drafting. The second is reviewing too late, after the search has already run everywhere, so a logic error has to be fixed and rerun across every database rather than corrected once on the master strategy. The third is checking only the lead database and assuming the translations inherited its quality, when translation introduces fresh syntax and heading errors of its own. Peer reviewing the primary strategy early, with a fresh expert, and rechecking high-stakes translations is what makes the step deliver, and it is the search-stage counterpart of the duplicate screening that follows.

Peer Review of Search Strategies: The PRESS Checklist