Echocardiography, endocarditis, and clinical information bias.

Although clinical information provided to the interpreter of imaging tests may improve disease detection, it may also bias the interpreter towards certain diagnoses, increasing the chance of false positives. To determine the possibility of this bias, the authors studied patients who were referred for echocardiography with a clinical suspicion of endocarditis. Hospital charts from a two-year period were reviewed to determine clinical data available to the echocardiographer, echocardiogram results, and the final diagnosis. Four clinical features, when present at the time of echocardiography, were associated with increased numbers of false-positive results. Test specificity was 97% (34/35) for patients without any of these features, but dropped to 80% (16/20) when two or more features were present. The authors conclude that clinical information may bias echocardiogram interpretations such that both test specificity and the posttest probability of disease may be overestimated when tests are used in clinical practice.