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8.1 Search strategy design and evaluation

In a literature review, it is important that the data search is carefully designed and written as a search term. The starting point for formulating a search strategy is the research question: what do you want the review to answer? The main concepts of the topic are derived from the question and their counterparts are searched for in the subject and keywords. The objective of the search determines how comprehensive the search is to be. The most important thing when conducting a literature review is to find enough sources that answer the research question satisfactorily (Marjamaa & Sinisalo 2022). The Systematic Search Guide made by Tampere University Library is a great source for learning about search strategy design and evaluation.

The search term is formed from ideated words using basic search tools:

  • Boolean operators AND, OR, NOT
  • Parentheses
  • Truncation
  • Phrases
  • Proximity operators

Most databases use Boolean operators to combine search words. The AND operator is used to combine different search sets, while the OR operator is used to combine alternative words. A good rule of thumb is to have no more than three AND operators in a search clause. The NOT operator can be used to exclude something from the search results, but care must be taken when using it. For example, NOT cancer will also remove search results that contain the word combination cancer free (Lehtiö, Johansson 2016, 38-39).

Each database works slightly differently, so the basic expression needs to be adapted to suit each database. The adaptation of the search to different databases must be described clearly enough. The adaptation of the search takes into account the characteristics of each database, such as the keyword delimiter, the vocabulary contained in the database, the way phrases are searched, the use of operators provided by the database, such as Boolean operators or proximity operators (NEAR). It is always worth checking the database for more detailed instructions (cf. Lehtiö, Johansson 2016, 42-43). In many databases, the search history view allows you to combine different search sets from different rows using AND or OR operators.

The checklist allows the evaluation of the data search strategy after the test searches, before the actual data searches are carried out. When choosing search terms, consideration should be given to whether to use a combination of subject and/or own terms. Sometimes a hierarchical structure of subject headings, showing broader and narrower concepts, can be useful. For example, if the key term for a topic cannot be found in the glossary or in the search results of a database, it may be worth considering whether a more general term would be a good search term, using the more specific term as an entry criterion. For example, rehabilitation as a broader search term, social rehabilitation as an entry criterion to exclude other types of rehabilitation at the title level and in the selection of abstracts. It may not be a good idea to pile up everything into complex search terms, but to use three-step screening (title, subject headings and summary, full text) with inclusion and exclusion criteria (cf. Valkeapää 2016, 56-58, 61-62).

Literature review search strategy checklist


Research question formulation (e.g. using PICO) :

  • Does the search strategy match the research question?
  • Are the search concepts clear?
  • Are there too many search terms?
  • Are any of the search concepts too narrow or broad?
  • Does the search produce too many or too few results?


Boolean operators AND, OR, NOT, brackets ()

  • Is there a need to improve the use of operators?
  • Is there a problem with combining words with brackets?
  • If NOT/NOT is used, can the essential be truncated?
  • Could the AND/AND operator be replaced by something more specific (proximity searches)?


Keywords (YSA, Mesh, Cinahl headings, etc.)

  • Are the keywords relevant?
  • Are some keywords missing?
  • Are any subject headings too narrow or too broad?  Are expansions (explode) and subheadings used sensibly?
  • Are you looking for both subject headings and free-language words? – If not, is there a reasonable justification?


Free-text words (free-text, keywords)

  • Are alternative/legal spellings of words taken into account?
  • Are synonyms taken into account?
  • Is the keyword missing or in the right place?
  • Have abbreviations been expanded?
  • Have overly broad or clearly irrelevant search terms been used?


Delimiters and filters

  • Do any of the delimiters seem unnecessary?
  • Have filters been used appropriately for the topic?
  • Are any relevant delimiters or filters missing?


Adapting the search strategy to different databases

  • Are the databases selected appropriately? Note! several foreign ones too!
  • Can the applicant demonstrate the applicability of the search strategy to different databases?
  • Are the applications of the search strategy to different databases available/visible for evaluation?

Source:

McGowan, J., Sampson, M. & Lefebvre, C. 2010. An Evidence Based Checklist for the Peer Review of Electronic Search Strategies (PRESS EBC). Evidence Based Library and Information Practice 5.1, 149–154. 


Other literature:

McGowan, J., Sampson, M., Salzwedel, D. M., Cogo, E., Foerster, V., & Lefebvre, C. (2016). PRESS Peer Review of Electronic Search Strategies: 2015 Guideline Statement. Journal of clinical epidemiology,75,40–46. https://doi.org/10.1016/j.jclinepi.2016.01.021. Päivitetty PRESS 2015 Guideline Statement sisältää dokumentit: PRESS 2015 Evidence-Based Checklist, PRESS 2015 Recommendations for Librarian Practice, PRESS 2015 Implementation Strategies, ja PRESS 2015 Guideline Assessment Form

The respective Finnish site translated in English 10.3.2025 / Riikka Ahlgren

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