Cardiac computed tomography-not ready for prime time

Objective, To establish the diagnostic accuracy of multidetector computed tomography (CT) angiography for identifying symptomatic patients with suspected coronary artery disease (CAD) who should be referred for coronary angiography, Design. Multicenter, prospective cohort study Setting and participants. 405 patients aged ≥ 40 years recruited from 9 hospitals in 7 countries. Patients with a history of cardiac surgery, elevated serum creatinine, organ transplantation, dye allergy, aortic stenosis, atrial fibrillation, New York Heart Association class III or IV heart failure, coronary angiography within the last 6 months, and body mass index > 40 kg/m² were excluded. Intervention. Patients underwent 2 multidetector CT tests (coronary calcium scoring and CT angiography) before conventional coronary angiography was performed. Raw image data sets from all acquisitions were analyzed by an independent core laboratory. Two independent observers visually graded the nonstented segments that were ≥ 1.5 mm in diameter. Conventional coronary angiography was performed within 30 days of CT angiography. All coronary segments ≥ 1.5 mm in diameter were analyzed using the 29-segment standard model. Main outcome measures. Diagnostic accuracy of CT angiography as compared with the gold standard conventional coronary angiography, evaluated using the modified Duke coronary artery score and measured as the area under the receiver operating curve (AUC). Clinically significant stenosis was defined as ≥ 50% stenosis in ≥ 1 vessel. Main results. Among the 405 patients enrolled, only 291 were included in the analysis. 89 patients had Agatston calcium scores > 600 and were excluded. Another 25 patients were excluded because coronary angiography was cancelled or technical failure of CT angiography. 56% of patients had obstructive CAD. The AUC for CT angiography was 0.93 (95% confidence interval [CI], 0.90-0.96) for the diagnosis of a patient with ≥ 1 coronary stenosis of ≥ 50% as determined by coronary angiography. The sensitivity for detecting obstruc- tive stenosis was 85% (95% CI, 79%-90%) and specificity was 90% (95% CI, 83%-94%). The positive and negative predictive values were 91% (95% CI, 86%-95%) and 83% (95% CI, 75%-89%), respectively, for a disease prevalence of 56%. Conclusion. Although the diagnostic performance of CT angiography was close to that of conventional coronary angiography, the negative predictive value of 83% suggests that 1 of 6 patients would be incorrectly diagnosed as not having CAD when in fact they did. CT angiography cannot replace coronary angiography in assessing the presence of obstructive stenosis.