The absence of coronary calcification may dupe readers into dismissing signs of obstructive coronary artery disease (CAD) on CT angiography (CTA) scans. That is one of several predictors of diagnostic inaccuracies identified in a study published in the Journal of the American College of Cardiology Cardiovascular Imaging’s September issue.

The American College of Cardiology, the Society of Cardiovascular Computer Tomography, the European Society of Cardiology and other organizations have recognized the benefit of CTA as a diagnostic tool for obstructive CAD. CTA offers a noninvasive alternative to quantitative coronary angiography to evaluate patients with low to intermediate probability of CAD.

But its value hinges on accurate interpretation of scans. Raymond T. Yan, MD, of Johns Hopkins Hospital in Baltimore, and colleagues explored factors that influence inaccurate diagnosis, focusing on patient clinical characteristics and coronary artery segments. For their analysis, they used the Coronary Artery Evaluation Using 64-Row Multi-detector Computed Tomography Angiography (CorE-64) study, which compared the diagnostic accuracy of CTA and quantitative coronary angiography.

The study enrolled 291 patients from nine centers who were referred for invasive coronary angiography. It defined significant obstructive CAD as luminal diameter narrowing of 50 percent or more as detected on quantitative coronary angiography.

Yan et al’s analysis looked at overall diagnostic inaccuracies on patient- and segment-based levels, stratified by the presence or absence of obstructive CAD. They found that the presence of coronary calcification and a higher Agatston calcium score independently increased the odds of a false positive diagnosis. On the other hand, the absence of within-segment calcification independently predicted a false negative diagnosis.

“In the present study, we establish the absence of coronary calcification as an underappreciated independent risk marker for FN [false negative] diagnoses,” they wrote. “Our results suggest that the absence of calcification may reduce a reader’s vigilance for stenosis and that potential lesions without obvious (i.e., calcified) evidence of atherosclerosis may be dismissed as artifacts.”

At the segment level, Yan et al identified smaller luminal caliber, segment tortuosity, suboptimal intra-arterial contrast enhancement and juxta-arterial vein conspicuity as features independently associated with misdiagnoses.

The authors cautioned that the number of misdiagnosed patients in the study was “modest” and that patent-level associations needed to be confirmed in larger studies.