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.
For more information:
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.