January 19th, 2012
CT Angiography Found Less Helpful in Patients With High Calcium Scores
Computed tomography angiography (CTA) has been proposed as a less invasive method to exclude obstructive coronary artery disease (CAD), but no consensus has been achieved about its clinical role in different patient subsets. Now a new report published in JACC from the CORE-64 (Coronary Artery Evaluation Using 64-Row Multidetector Computed Tomography Angiography) study shows that CTA may not be worthwhile in people with a calcium score of 600 or above or who already have a high pre-test probability of having CAD.
The CORE-64 investigators compared CTA and quantitative coronary angiography (QCA) in 371 patients. (A previous report published in NEJM excluded 80 patients with a calcium score of 600 or above.) They found that CTA accurately ruled out obstructive CAD in two groups:
- patients with low coronary calcium scores and with a low or intermediate pre-test risk of CAD
- patients with a calcium score of 0 with any pre-test risk of CAD
The negative predictive value of CTA in the group of patients with calcium scores of 600 or greater was 0.50 (0.16-0.84).
In an accompanying editorial, Steve Nissen writes that the study findings suggest that CTA “probably should not be used for diagnostic purposes in patients with substantial coronary calcification.” Nissen also points out that “the radiation dose from CTA is equivalent to 3 to 7 diagnostic catheterizations.” Until CTA is more fully evaluated in clinical trials, writes Nissen, “coronary imaging using CTA should be used sparingly, with full recognition of the radiation burdens and risks of misdiagnosis.”