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Review
. 2012 Jun 12;14(3):e85.
doi: 10.2196/jmir.2021.

Sensitivity and predictive value of 15 PubMed search strategies to answer clinical questions rated against full systematic reviews

Thomas Agoritsas  1 , Arnaud Merglen, Delphine S Courvoisier, Christophe Combescure, Nicolas Garin, Arnaud Perrier, Thomas V Perneger
Affiliations
Review

Sensitivity and predictive value of 15 PubMed search strategies to answer clinical questions rated against full systematic reviews

Thomas Agoritsas et al. J Med Internet Res. .

Abstract

Background: Clinicians perform searches in PubMed daily, but retrieving relevant studies is challenging due to the rapid expansion of medical knowledge. Little is known about the performance of search strategies when they are applied to answer specific clinical questions.

Objective: To compare the performance of 15 PubMed search strategies in retrieving relevant clinical trials on therapeutic interventions.

Methods: We used Cochrane systematic reviews to identify relevant trials for 30 clinical questions. Search terms were extracted from the abstract using a predefined procedure based on the population, interventions, comparison, outcomes (PICO) framework and combined into queries. We tested 15 search strategies that varied in their query (PIC or PICO), use of PubMed's Clinical Queries therapeutic filters (broad or narrow), search limits, and PubMed links to related articles. We assessed sensitivity (recall) and positive predictive value (precision) of each strategy on the first 2 PubMed pages (40 articles) and on the complete search output.

Results: The performance of the search strategies varied widely according to the clinical question. Unfiltered searches and those using the broad filter of Clinical Queries produced large outputs and retrieved few relevant articles within the first 2 pages, resulting in a median sensitivity of only 10%-25%. In contrast, all searches using the narrow filter performed significantly better, with a median sensitivity of about 50% (all P < .001 compared with unfiltered queries) and positive predictive values of 20%-30% (P < .001 compared with unfiltered queries). This benefit was consistent for most clinical questions. Searches based on related articles retrieved about a third of the relevant studies.

Conclusions: The Clinical Queries narrow filter, along with well-formulated queries based on the PICO framework, provided the greatest aid in retrieving relevant clinical trials within the 2 first PubMed pages. These results can help clinicians apply effective strategies to answer their questions at the point of care.

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Conflict of interest statement

None declared.

Figures

Figure 1
Figure 1
Framework for PubMed search strategies to answer clinical questions. AIM = Abridged Index Medicus (set of 119 core clinical journal titles [28]), EBM = evidence-based medicine, MeSH = Medical Subject Headings (a controlled vocabulary used for indexing articles in PubMed), PICO = population, interventions, comparison, outcomes.
Figure 2
Figure 2
Definitions of the sensitivity and positive predictive value (PPV) of search strategies, when using a systematic review as the gold standard. a We included only the studies published before the date when the corresponding systematic review was assessed as up-to-date. b We excluded from this total the studies that are not indexed in PubMed, as they cannot be retrieved by any search strategy. c This total is unknown, because it is not limited to the studies that were explicitly excluded from the systematic review. d When only a limited number of items in the output are screened (eg, 40 items, or 2 pages of PubMed’s output), then practically this number becomes the true denominator of PPV.
Figure 3
Figure 3
Compared sensitivity and positive predictive value (PPV) of the 15 search strategies (S) tested, for (A) the full search output and (B) the first 2 PubMed pages (40 articles). CQ = Clinical Queries, PIC(O) = population, interventions, comparison, (outcomes).
Figure 4
Figure 4
Evolution of median sensitivity of the search according to the number of studies screened in the output for the unfiltered population, interventions, comparison (PIC) query (S1) and the PIC query filtered by the Clinical Queries (CQ) narrow filter (S4).
See this image and copyright information in PMC

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