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As mentioned in the “Marathon Man” Case #345, I like imaging — both invasive and non-invasive — for accurate CAD risk assessment. But no test is perfect, including the Coronary Artery Calcium (CAC) scan, which provides us with the CAC score (CACS).
In this interesting JACC article*, published February 16, 2010, 24 percent of people presenting with symptoms consistent with coronary occlusion had a CACS of zero. Nineteen percent of people with no calcium (calcified plaque) had >= 50% stenosis, and 20 percent of complete occlusion arteries had no calcium. Note the sensitivity and specificity as well as the sensitivity and specificity as well as negative and positive predictive value. A nice review of the journal article can be read at Reviews in Cardiovascular Medicine (free registration).
The CAC score is a valuable tool and improves risk assessment. However, the CACS gives “false negatives” of 55 percent — zero score, yet clinically significant soft plaque burden and/or stenosis. When we see CACS positive patients in our practice, we know they have atherosclerosis. When we see CACS negative patients, we know they can still have athero. In this paper, for patients presenting with CAD symptoms, 19 percent with CACS of zero had stenosis that was significant.
*Gottlieb I, Miller J, Arab-Zadeh A, et al. The absence of coronary calcification does not exclude obstructive coronary artery disease or the need for revascularization in patients referred for conventional coronary angiography. J Am Coll Cardiol 2010; 44:627-34.
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