Comparison of exercise test scores and physician estimation in determiningdisease probability

Background: The recent American College of Cardiology/ American Heart Assoc iation exercise testing guidelines provided equations to calculate treadmil l scores and recommended their use to improve the predictive accuracy of th e standard exercise test. However, if physicians can estimate the probabili ty of coronary artery disease as well as the scores can, there would be no reason to add this complexity to test interpretation. To compare the exerci se test scores with physician's estimation of disease probability, we used clinical, exercise test, and coronary angiographic data to compute the reco mmended scores and print patient summaries and treadmill reports. Objective: To determine whether exercise test scores can be as effective as expert cardiologists in diagnosing coronary disease. Methods: Five hundred ninety-nine consecutive male patients without previou s myocardial infarction with a mean +/- SD age of 59 +/- 11 years were cons idered for this analysis. With angiographic disease defined as any coronary lumen occlusion of 50% or more, 58% had disease. The clinical/treadmill te st reports were sent to expert cardiologists and to 2 other groups, includi ng randomly selected cardiologists and internists, who classified the patie nts as having high, low, or intermediate probability of disease and estimat ed a numerical probability from 0% to 100%. Results: Forty-five expert cardiologists returned estimates on 336 patients , 37 randomly chosen practicing cardiologists returned estimates on 129 pat ients, 29 randomly chosen practicing internists returned estimates on 106 p atients, 13 academic cardiologists returned estimates on 102 patients, and 27 academic internists returned estimates on 174 patients. When probability estimates were compared, the scores were superior to all physician groups (0.76 area under the receiver operating characteristic curve to 0.70 for ex perts [P=.046], 0.73 to 0.58 for cardiologists [P=.003], and 0.76 to 0.61 f or internists [P=.006]). Using a probability cut point of greater than 70% for abnormal, predictive accuracy was 69% for scores compared with 64% for experts, 63% to 62% for cardiologists, and 70% to 57% for internists. Conclusion: Although most similar to the disease estimates of the presence of clinically significant angiographic coronary artery disease provided by the expert cardiologists, the scores outperformed the nonexpert physicians.