Incremental prognostic power of clinical history, exercise electrocardiography and myocardial perfusion scintigraphy in suspected coronary artery disease

The incremental ability of a clinical history, exercise electrocardiography (ECG) and myocardial perfusion scintigraphy to identify coronary events in the year after testing was assessed in 1,659 patients with symptoms suggestive of coronary artery disease (CAD), 74 of whom suffered a coronary event in the year after testing. Prognostic power was quantified in terms of the area under receiver operating characteristic curves derived from logistic regression. In 1,451 patients with normal rest ECG findings, a clinical history alone provided the most prognostic power (area = 72%). This improved significantly (by 5%) only when both tests were analyzed. In contrast, clinical history had significantly less prognostic power in the 208 patients with abnormal rest ECG findings (area = 58%), but each test then provided a significant incremental improvement in these patients (by 14% for each). A strategic model was thereby developed for prognostic assessment that recognizes the incremental power of these tests in specific patient groups as well as their overall accuracy and monetary cost. This strategy stratified individual patient risk for subsequent coronary events over a full order of magnitude (from 2 to 22%) at a 64% reduction in the cost of testing compared to performing both stress tests in all patients.