Absolute coronary artery calcium score is the best predictor of non-calcified plaque involvement in patients with low calcium scores (1-100).

Objective: We sought to identify the predictors of non-calcified plaque (NCP) burden in patients with low coronary artery calcium (CAC) scores of 1-100.

Methods: We studied 920 consecutive patients clinically referred for coronary CT angiography (CCTA) with concomitant CAC scoring. The 276 patients with CAC 1-100 were divided into four groups based on the CAC score: CAC = 0, 1-10, 11-50, and 51-100. Univariate and multivariate linear regression analyses were performed for the demographic, risk factor, and CAC score predictors of number of coronary segments with NCP.

Results: Mean age was 55 ± 11 years and 56% were women. Demographics and risk factors failed to identify NCP involvement in univariate models. The lone predictor of NCP burden was the absolute CAC score, which was persistently associated with NCP in multivariable models (CAC 51-100 vs. CAC 1-10, β-coefficient 0.35, p = 0.03).

Conclusions: Absolute CAC score is the lone robust predictor of NCP burden when CAC is 1-100. Risk within this mild coronary calcification group is likely heterogeneous, driven by the absolute CAC score.