Abstract
BACKGROUND: We determined whether high-sensitivity cardiac troponin I can improve the estimation of the pretest probability for obstructive coronary artery disease (CAD) in patients with suspected stable angina. METHODS AND RESULTS: In a prespecified substudy of the SCOT-HEART trial (Scottish Computed Tomography of the Heart), plasma cardiac troponin was measured using a high-sensitivity single-molecule counting assay in 943 adults with suspected stable angina who had undergone coronary computed tomographic angiography. Rates of obstructive CAD were compared with the pretest probability determined by the CAD Consortium risk model with and without cardiac troponin concentrations. External validation was undertaken in an independent study population from Denmark comprising 487 patients with suspected stable angina. Higher cardiac troponin concentrations were associated with obstructive CAD with a 5-fold increase across quintiles (9%-48%; P<0.001) independent of known cardiovascular risk factors (odds ratio, 1.35; 95% confidence interval, 1.25-1.46 per doubling of troponin). Cardiac troponin concentrations improved the discrimination and calibration of the CAD Consortium model for identifying obstructive CAD (C statistic, 0.788-0.800; P=0.004; χ(2)=16.8 [P=0.032] to 14.3 [P=0.074]). The updated model also improved classification of the American College of Cardiology/American Heart Association pretest probability risk categories (net reclassification improvement, 0.062; 95% confidence interval, 0.035-0.089). The revised model achieved similar improvements in discrimination and calibration when applied in the external validation cohort. CONCLUSIONS: High-sensitivity cardiac troponin I concentration is an independent predictor of obstructive CAD in patients with suspected stable angina. Use of this test may improve the selection of patients for further investigation and treatment. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01149590.