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Usefulness of CTA varies widely based on patient population
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Pretest probability for coronary artery disease and coronary calcium score should be considered before using CTA for excluding coronary artery disease, researchers for the CORE-64 trial reported.
The Coronary Artery Evaluation Using 64-Row Multidetector Computed Tomography Angiography (CORE-64) trial included 371 patients (mean age, 61 years; 75% men) who underwent CTA and cardiac catheterization for the detection of obstructive CAD. All enrolled patients were aged at least 40 years, had suspected symptomatic CAD and had a referral for conventional coronary angiography.
Ability of test to predict, exclude disease
According to an analysis of patient-based quantitative CTA accuracy, the area under the receiver-operating characteristic curve (AUC) was 0.93 (95% CI, 0.90-0.95); the AUC remained 0.93 after exclusion of patients with known CAD. The AUC decreased to 0.81 (95% CI, 0.71-0.89) in patients with calcium scores of at least 600 (P=.077). Results showed similar AUCs in patients with intermediate (0.93), high pretest probability for CAD (0.92) and known CAD (0.93), whereas negative predictive values were different in these groups (0.9, 0.83 and 0.5, respectively). In patients with calcium scores of less than 100 or 100 or more, negative predictive values decreased from 0.93 to 0.75 (P=.053).
“Cardiac CTA is a powerful diagnostic tool in patients with moderate or high probability for presence of obstructive CAD,” Joao A. C. Lima, MD, of the division of cardiology at Johns Hopkins University, told Cardiology Today. “The AUC is reduced from the low 90s to the low 80s in patients with high calcium scores, reflecting the loss of diagnostic power, particularly if one wants to exclude obstructive disease in those patients.”
Armin Arbab-Zadeh, MD, PhD, also of the division of cardiology at Johns Hopkins University, said, “Predictive values critically depend on the disease prevalence in the study population. Our study demonstrates how a test with very good diagnostic accuracy performs differently in populations with different disease prevalence.”
Applying coronary CTA in clinical practice
In an accompanying editorial, Steven E. Nissen, MD, of the Cleveland Clinic Foundation and Cardiology Today Editorial Board member, said: “The careful analysis provided by the current study will be valuable to practitioners considering how to optimally apply coronary CTA in routine clinical practice. These findings suggest that CTA — using current technology — probably should not be used for diagnostic purposes in patients with substantial coronary calcification.
“In determining when to use coronary CTA in clinical practice, we must also consider the potential harm produced by coronary CTA imaging as currently practiced. The doses of radiation are substantial, although gradually falling at sophisticated centers with technical improvements in study methods,” Nissen wrote.
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Disclosure: Dr. Arbab-Zadeh reports serving on the steering committee of the CORE-320 study, sponsored by Toshiba Medical Systems. Dr. Lima is the chairman of the steering committee of the CORE-320 study and received grant support from Bracco Diagnostics, GE Medical Systems and Toshiba Medical Systems. Dr. Nissen reports no relevant financial disclosures.
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