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Searching is an iterative process. The researcher or clinician determines whether the searched primary, secondary, and tertiary information resources have responsibly addressed the research topic or clinical dilemma. When completing a database search, it is important to achieve a balance between precision (or specificity) and recall (or sensitivity).
The following table outlines different search techniques that can increase precision or recall of the literature search.
Too Many Results (increase precision or specificity) | Too Few Results (increase recall or sensitivity) |
---|---|
Use major subject terms | Use the broad subject terms |
Use the "focus" option, if available | Use the "explode" option, if available |
Select more specific, narrower subject headings | Check similar/related articles for additional terms |
Use appropriate subheadings for each subject heading | Do not use subject heading’s subheadings |
Decrease the number of keywords, synonyms | Use the database's search fields to identify keywords |
Precision can be enhanced by decreasing the use of the Boolean operator "OR". This eliminates synonyms or like concepts. | Include alternate spellings, variant endings |
Precision can also be increased by adding concepts with the Boolean operator "AND". | Increasing recall requires greater use of synonyms and the Boolean operator "OR", as well as a reduction in the use of the Boolean operator "AND". |
Searching for precision should result in retrieving many relevant citations and very few irrelevant citations. | Be aware that recall will have an inverse effect on the performance of the literature search by also retrieving many irrelevant citations. |
(Allison, Kiefe, Weissman, Carter, & Centor, 1999; Jankowski, 2008; McKibbon & Walker-Dilks, 1995; Wessel, 2019)
The database’s search history feature is essential to keep track of the search strategy. This feature allows the searcher to use Boolean operators to combine – and recombine – search lines and apply limits or filters to refine search results. Additionally, the searcher can use the search history to translate the search strategy to other databases, i.e., from PubMed/Ovid MEDLINE to Ovid Embase.
As expected, since PubMed and Ovid MEDLINE search the same records, there is minimal difference in the number of citations retrieved.
When translating the search to Embase, notice the different subject headings as well as the number of citations retrieved. It is not unusual for the Embase search to retrieve more results than PubMed/Ovid MEDLINE as the Emtree subject headings are more granular than MeSH.
(Gray, 2012; U.S. National Library of Medicine, 2019; Wessel, 2019; Wolters Kluwer, 2019)
See Appendix 3 - Database Comparison Chart to view a chart that summarizes search tips by commonly searched databases. This tool is helpful when translating a search from one database to another database.
(Elsevier, 2019; Jankowski, 2008; Patrick & Munro, 2004; U.S. National Library of Medicine, 2019; Welch Medical Library, 2019; Wolters Kluwer, 2019)
Most databases have output choices, which can include but not be limited to:
Citation management software, such as EndNote (UT Southwestern campus standard), RefWorks, Zotero, Mendeley, etc. allow the user to:
Refer to the specific database handout for information related to output, saved searches, and alerts.
(Gray, 2012; U.S. National Library of Medicine, 2019; Wessel, 2019; Wolters Kluwer, 2019)
Many databases permit the searcher, researcher, or clinician to create an account to save the search strategy and/or create an alert to receive scheduled updates. Retrieving and re-running a saved search saves time and allows the searcher, researcher, or clinician to edit and document changes to the search strategy. Depending on the database, the user can schedule the frequency of the alert, report format, number of citations to send, etc.
Refer to the specific database handout for information related to output, saved searches, and alerts.
(Gray, 2012; U.S. National Library of Medicine, 2019; Wessel, 2019; Wolters Kluwer, 2019)
Allison, J. J., Kiefe, C. I., Weissman, N. W., Carter, J., & Centor, R. M. (1999). The art and science of searching MEDLINE to answer clinical questions. Finding the right number of articles. Int J Technol Assess Health Care, 15(2), 281-296.
Gray, J. R., Grove, S.K., and Burns, N. (2012). The practice of nursing research: Appraisal, synthesis, and generation of evidence. London: Elsevier Health Sciences.
Jankowski, T. A. (2008). The Medical Library Association Essential Guide to Becoming an Expert Searcher: Proven Techniques, Strategies, and Tips for Finding Health Information. New York: Neal-Schuman Publishers.
McKibbon, K. A., & Walker-Dilks, C. J. (1995). The quality and impact of MEDLINE searches performed by end users. Health Libr Rev, 12(3), 191-200. doi:10.1046/j.1365-2532.1995.1230191.x
U.S. National Library of Medicine. (2019, November 15, 2019). PubMed User Guide. Retrieved from https://pubmed.ncbi.nlm.nih.gov/help/
Wessel, C. B. (2019). Responsible Literature Searching for Research: A Self-Paced Interactive Program. Retrieved from https://cme.hs.pitt.edu/ISER/app/learner/loadModule?moduleId=8381&dev=false
Wolters Kluwer. (2019). Ovid Help. Retrieved from http://site.ovid.com/site/help/documentation/osp/en/index.htm#CSHID=advanced.htm