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Systematic Reviews: PRESS - Checklist for Search Strategies

An introductory guide to Systematic Reviews


As the literature search is a fundamental part of a systematic review, it's important that the search strategy is of high quality. To ensure this, and to avoid errors, there are several options. One option is to involve an experienced librarian/ information specialist in the review project. It is recommended if a second person has a thorough look at the search strategy.

There is also a tool for validating search strategies called Peer Review of Electronic Search Strategies (PRESS).

PRESS was originally published in 2008–2010, but was revised in 2015. The PRESS checklist was originally made for expert searchers, such as librarians, but can also be used by students and researchers when creating more extensive search strategies. The evidence and conclusions in PRESS are based on a comprehensive research project.

Karolinska Institutet University Library (2022). Systematic reviews [PRESS] :,

PRESS 2015 checklist for search strategies

Translation of the research question

  • Does the search strategy match the research question/PICO?
  • Are the search concepts clear?
  • Are there too many or too few PICO elements included?
  • Are the search concepts too narrow or too broad?
  • Does the search retrieve too many or too few records? (Please show number of hits per line.)
  • Are unconventional or complex strategies explained?

Boolean and proximity operators

These vary based on search service

  • Are Boolean or proximity operators used correctly?
  • Is the use of nesting with brackets appropriate and effective for the search?
  • If NOT is used, is this likely to result in any unintended exclusions?
  • Could precision be improved by using proximity operators (e.g., adjacent, near, within) or phrase-searching instead of AND?
  • Is the width of proximity operators suitable (e.g., might adj5 pick up more variants than adj2)?

Subject headings


  • Are the subject headings relevant?
  • Are any relevant subject headings missing; e.g., previous index terms?
  • Are any subject headings too broad or too narrow?
  • Are subject headings exploded where necessary and vice versa?
  • Are major headings (“starring” or restrict to focus) used? If so, is there adequate justification?
  • Are subheadings missing?
  • Are subheadings attached to subject headings? (Floating subheadings may be preferred.)
  • Are floating subheadings relevant and used appropriately?
  • Are both subject headings and terms in free text (see below) used for each concept?

Text word searching

Free text

  • Does the search include all spelling variants in free text (e.g., UK versus US spelling)?
  • Does the search include all synonyms or antonyms (e.g., opposites)?
  • Does the search capture relevant truncation (i.e., is truncation at the correct place)?
  • Is the truncation too broad or too narrow?
  • Are acronyms or abbreviations used appropriately? Do they capture irrelevant material? Are the full terms also included?
  • Are the keywords specific enough or too broad? Are too many or too few keywords used? Are stop words used?
  • Have the appropriate fields been searched; e.g., is the choice of the text word fields (.tw.) or all fields (.af.) appropriate? Are there any other fields to be included or excluded (database-specific)?
  • Should any long strings be broken into several shorter search statements?

Spelling, syntax and line numbers

  • Are there any spelling errors?
  • Are there any errors in system syntax; e.g., the use of a truncation symbol from a different search interface?
  • Are there incorrect line combinations or orphan lines (i.e., lines that are not referred to in the final summation that could indicate an error in an AND or OR statement)?

Limits and filters

  • Are all limits and filters used appropriately and are they relevant given the research question?
  • Are all limits and filters used appropriately and are they relevant for the database?
  • Are any potentially helpful limits or filters missing? Are the limits or filters too broad or too narrow? Can any limits or filters be added or taken away?
  • Are sources cited for the filters used?


McGowan J, Sampson M, Salzwedel DM, Cogo E, Foerster V, Lefebvre C. (2016). PRESS Peer Review of Electronic Search Strategies: 2015 Guideline Statement. J Clin Epidemiol. Jul;75:40–46
(2016). PRESS – Peer Review of Electronic Search Strategies: 2015 Guideline Explanation and Elaboration (PRESS E&E). Ottawa: CADTH.