Optimal search strategies for retrieving scientifically strong studies of diagnosis from Medline: analytical survey

OBJECTIVE: To develop and test optimal Medline search strategies for retrieving sound clinical studies on prevention or treatment of health disorders. DESIGN: Analytical survey. DATA SOURCES: 161 clinical journals indexed in Medline for the year 2000. MAIN OUTCOME MEASURES: Sensitivity, specificity, precision, and accuracy of 4862 unique terms in 18 404 combinations. RESULTS: Only 1587 (24.2%) of 6568 articles on treatment met criteria for testing clinical interventions. Combinations of search terms reached peak sensitivities of 99.3% (95% confidence interval 98.7% to 99.8%) at a specificity of 70.4% (69.8% to 70.9%). Compared with best single terms, best multiple terms increased sensitivity for sound studies by 4.1% (absolute increase), but with substantial loss of specificity (absolute difference 23.7%) when sensitivity was maximised. When terms were combined to maximise specificity, 97.4% (97.3% to 97.6%) was achieved, about the same as that achieved by the best single term (97.6%, 97.4% to 97.7%). The strategies newly reported in this paper outperformed other validated search strategies except for two strategies that had slightly higher specificity (98.1% and 97.6% v 97.4%) but lower sensitivity (42.0% and 92.8% v 93.1%). CONCLUSION: New empirical search strategies have been validated to optimise retrieval from Medline of articles reporting high quality clinical studies on prevention or treatment of health disorders.