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.