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Systematic and Complex Reviews

Steps in a systematic review literature search

  1. Select a framework (PICO, SPIDER etc).
  2. Use the framework to design or analyze your researchable question.
  3. Record inclusion and exclusion criteria.
  4. Identify free text terms and index terms relevant to each concept in your framework. Generate related terms and synonyms for free text terms. Ensure your search terms are consistent with your research question.
  5. Conduct a preliminary search across one or two databases to identify additional subject terms or free text terms. 
  6. Decide: Which search terms will be truncated, will wild cards, proximity operators, or phrase searching be used? This will create your search statement for each concept in your table.
  7. Decide if a date and/or language restriction will be applied to search results. Ideally no language restrictions should be applied.
  8. Select a database for searching and decide which fields will be searched for results.
  9. Conduct a comprehensive search for each separate concept in your framework using its search statement and selected fields. Apply boolean operators appropriately to combine terms within each search statement.
  10. Utilize the search history and/or appropriate boolean operators to combine the completed searches for each of the separate concepts from the your selected framework in the selected database.
  11. Apply database limiting commands (date, study types). Decide if search filters are required.
  12. Export results to your reference manager.
  13. Save a record of the search. Note the platform used and the date of the search.

Conduct searches across multiple relevant databases. Adapt searches to the characteristics of the database. Document any modifications when adapting your search to a new database e.g. Are the fields different? Does the database use different subject headings? Conduct supplementary searches across grey literature, as well as hand searching selected journals and by citation tracking to address bias from published results. ​

Whenever possible consult with a librarian in regard to your search strategy and refer to tutorials and guidelines below.

Tutorials and guidelines

Precision vs Sensitivity

When searching for material for systematic reviews there is a tension between comprehensiveness (SENSITIVITY) and relevance (PRECISION). In general the more comprehensive the search the less relevant are the results. 

​SENSITIVITY =  number of relevant reports identified/Total number of relevant reports in existence
​PRECISION =    number of relevant reports identified/Total number of reports identified (Cochrane Handbook for Systematic Reviews of Interventions).

​Developing a search strategy is an iterative process. Search terms are modified, based on what has already been retrieved. There are diminishing returns for search efforts; after a certain stage, each additional unit of time invested in searching returns fewer references that are relevant to the review. The decision as to how much to invest in the search process may depend on several factors, such as the question a review addresses, and the resources that are available.


Kugley, S., Wade, A., Thomas, J., Mahood, Q., Jørgensen, A.-M.K., Hammerstrøm, K., & Sathe, N. (2017). Searching for studies: A guide to information retrieval for Campbell systematic reviews. Campbell Systematic Reviews, 13(1), 1-73.

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