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Systematic Reviews, Scoping Reviews, and other Knowledge Syntheses

Search filters or hedges

Search filters, sometimes also called hedges or search blocks, are search strategies that usually include a series of pre-elaborated free-text terms/textwords/words/phrases plus subject headings for a given concept, idea, or study design; these search strategies have already been developed to find literature on the concept/idea/study design of interest within a particular database/platform (e.g., for the MEDLINE database on the Ovid platform). They may or may not have been validated for their sensitivity/specificity/precision, but when available, they are a useful tool to take advantage of work that others have already done to identify terms to find literature on a given concept.

If reusing search filters that others have developed, please cite or acknowledge them.

Useful sources of general search filters

Additional/more specific filters not listed above or suggested at McGill

In addition to using search filters or hedges, you may find it useful to consult other systematic reviews or knowledge syntheses related to at least one of the concepts of your search, to see how they developed the search strategy for the concept of interest. One trick, for example, is to search the Cochrane Library by restricting the term of interest to the title field in the record, and then looking at the search strategy in the full-text, as it is often well documented in Cochrane reviews. Ideally, you should check a few reviews given the quality of the searches can be quite heterogeneous.

Tools for developing a search strategy

These text mining tools can help you identify MeSH terms (subject headings in MEDLINE) related to a concept that you are including in your search strategy. It may be the case that you will have to use a combination of subject headings to capture a single concept.

Great tool for checking if brackets in single line searches are properly balanced

Enter the PubMed ID numbers of known relevant articles and create an HTML or Excel file indicating the MeSH headings used to index those articles.​

Harvey Cushing/John Hay Whitney Medical Library [Internet]. New Haven (CT): Yale Library; [cited 2021 Jan 15]. [Video], Yale MeSH Analyzer; [reviewed 2021 Jan 15, cited 2021 Jan 15]; [7 min., 39 sec]. Available from:

Enter a block of text and MeSH On Demand returns a list of MeSH Terms relevant to your text.

Have you found a line-by-line search strategy for an Ovid database that you would like to re-execute without copying and pasting each line into the search history? Try the Ovid Search History Launcher (if off campus, be sure to log in to McGill VPN beforehand)

  • Try copying and pasting the line-by-line strategy into a Word document > In Word, select all > Remove "numbering"
  • Copy this edited version and paste it into the Ovid Search History Launcher
  • Select Ovid MEDLINE ALL [medall] if searching MEDLINE and run the search

Useful for entering a high precision search on your topic or the PMIDs (PubMed unique identifiers) of articles that are relevant to your topic: PubReminer ranks the indexing terms (e.g., MeSH) or words that are most commonly associated with that set of records

See also: Text mining for searching and screening the literature

  • Look at the search strategies of other relevant knowledge syntheses

Look for syntheses that are about at least one of your concepts to see how other researchers developed their search strategies. Remember that search strategies are database and platform specific: e.g., an Ovid MEDLINE search strategy has to be built with its own syntax -- even if it uses MeSH -- and thus would have to be translated to PubMed, and vice-versa. Different databases, like Embase and PsycINFO for example, will also use their own subject headings: Be careful when reusing search strategies to make sure they are database and platform appropriate.

  • Check the indexing of relevant articles

If you have already found articles that your search should be picking up, copy and paste the article title into an article database like PubMed to see how it is indexed, if applicable.

Tools for translating a search strategy to other databases/platforms

The University of South Australia has some great guidance on running your searches on other databases.

Other tools

Search Translator: SRA Polyglot (use with caution)

With some caution, you can use the SRA Polyglot Search Translator to translate a PubMed or Ovid MEDLINE search strategy to several other databases/platforms, including CINAHL, Cochrane Library, Scopus, and Web of Science. 

Note that it will only translate the search syntax: It will NOT identify the equivalent subject headings in the other databases which include that feature. For example, continuity of patient care/ in Ovid MEDLINE will simply display as continuity of patient care/ for an Ovid Embase translation, but that will be run as patient care/, a broader concept, due to the absence of an EMTREE term for the concept of continuity of patient care. Be sure to identify the subject headings for each database and replace them as needed.

Note that the translation may leave some search fields that are either not available in another database or not recognized by the translator, e.g., child*.jw. will show up inappropriately in other database translations as child*.jw.

See: Clark JM, Sanders S, Carter M, Honeyman D, Cleo G, Auld Y, Booth D, Condron P, Dalais C, Bateup S, Linthwaite B, May N, Munn J, Ramsay L, Rickett K, Rutter C, Smith A, Sondergeld P, Wallin M, Jones M, Beller E. Improving the Translation of Search Strategies Using the Polyglot Search Translator: A Randomized Controlled Trial. J Med Libr Assoc. 2020;108(2):195-207. 10.5195/jmla.2020.834

See: Kung J. Polyglot Search Translator. Journal of the Canadian Health Libraries Association / Journal de l'Association des bibliothèques de la santé du Canada. 2022;43(1). 10.29173/jchla29600

Exclusion filters to selectively remove records

Use NOT statements with great care. We do not advise excluding records based on keyword searches.

Please note that these exclusion filters are database and platform-dependent (e.g., the exclusion filter for MEDLINE on PubMed will be different from the exclusion filter for MEDLINE on OvidSP because the platforms are searched differently).

Please note: Due to more reliance on automated indexing, particularly in MEDLINE, we are noticing an increase in errors that may lead to unintended effects when using these exclusion filters. We suggest not using exlusion filters, if feasible.

To remove studies indexed as animals only


  • not (exp animals/ not


  • NOT ("animals"[mesh] NOT "humans"[mesh])

Embase on OvidSP:

To remove studies indexed as child only


  • not ((exp infant/ or exp child/ or adolescent/) not (exp adult/))


  • NOT (("infant"[mesh] OR "child"[mesh] OR "adolescent"[mesh]) NOT "adult"[mesh])

Embase on OvidSP:

  • not (exp juvenile/ not exp adult/)

PsycInfo on Ovid SP:

  • NOT ((adolescence 13 17 yrs or childhood birth 12 yrs) not adulthood 18 yrs older).ag.


  • NOT ( ( (MH "Child+") OR (MH "Adolescence+") ) NOT (MH "Adult+") )

To remove studies indexed as adult only


  • not (exp adult/ not (exp infant/ or exp child/ or adolescent/))


  • NOT ("adult"[mesh] NOT ("infant"[mesh] OR "child"[mesh] OR "adolescent"[mesh]))

Embase on OvidSP:

  • not (exp adult/ not exp juvenile/)

PsycInfo on OvidSP:

  •  NOT     ((adulthood 18 yrs older) not (adolescence 13 17 yrs or childhood birth 12 yrs) ).ag.


  • NOT (MH "Adult+" NOT ( (MH "Child+") OR (MH "Adolescence+") ) ) 

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