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

OBJECTIVE: To develop optimal search strategies in Medline for retrieving sound clinical studies on the diagnosis of health disorders. DESIGN: Analytical survey. SETTING: Medline, 2000. PARTICIPANTS: 170 journals for 2000 of which 161 were indexed in Medline. MAIN OUTCOME MEASURES: The sensitivity, specificity, precision ("positive predictive value"), and accuracy of 4862 unique terms in 17,287 combinations were determined by comparison with a hand search of all articles (the "gold standard") in 161 journals published during 2000 (49,028 articles). RESULTS: Only 147 (18.9%) of 778 articles about diagnostic tests met basic criteria for scientific merit. Combinations of search terms reached peak sensitivities of 98.6% at a specificity of 74.3%. Compared with best single terms, best multiple terms increased sensitivity for sound studies by 6.8% (absolute increase), while also increasing specificity (absolute increase 6.0%) when sensitivity was maximised. When terms were combined to maximise specificity, the single term, specificity.tw. (98.4%), outperformed combinations of terms. The strategies newly reported in this paper outperformed other validated search strategies except for one strategy that had slightly higher sensitivity (99.3% v 98.6%) but lower specificity (54.7% v 74.3%). CONCLUSION: New empirical search strategies in Medline can optimise retrieval of articles reporting high quality clinical studies of diagnosis.