The 2018 AHA/ACC Multisociety Blood Cholesterol Guideline1 states that the use of coronary artery calcium (CAC) scoring is reasonable to inform statin therapy decision-making in those borderline or intermediate-risk patients with uncertainty about the need for statin therapy after consideration of risk-enhancing factors. The basis for its use rests on its ability to improve discrimination and reclassify risk as compared to that derived from risk equations based on traditional atherosclerotic cardiovascular disease (ASCVD) risk factors.2

Scans for CAC scoring are acquired using an axial mode with prospective ECG triggering during diastole. These images are then reconstructed, generally using 3 mm slices, to calculate the Agatston score, a technique in which the total CAC score is based on the amount and density of calcified plaque in all of the imaged coronary arteries.3 While CAC scoring is traditionally done using ECG gating, the finding of CAC on non-gated chest CT scans done for non-cardiac indications also provides diagnostic information that may be useful in statin therapy decision-making. The Society of Cardiothoracic Computed Tomography and the Society of Thoracic Radiology provide a Class I recommendation for interpreting physicians to provide qualitative interpretation of CAC on chest CT scans.3,4 Both Agatston scoring and manually calculated ordinal scoring for CAC on non-gated chest CT studies correlate well with EKG gated cardiac CT scores, provide high inter-reader correlation, and predict mortality,5 but may be difficult to fit into an already busy workflow.6,7

The fastest method is the visual estimation of CAC (Fig. 1) as either none, mild, moderate, or severe, findings that correlate well with Agatston scores and with mortality.8 The CAC-DRS (Coronary Artery Calcium Data and Reporting System) provides a standardized method for communicating CAC findings on all non-contrast CT scans using either Agatston or the visual estimation scoring methods.9 The identification of moderate or severe calcification correlates with a CAC score of ≥ 100 AU for which the AHA/ACC guidelines recommend a clinician-patient discussion on statin initiation.2,10,8 As non-cardiac chest CT imaging is done far more often than dedicated ECG-gated CAC scoring, CAC reporting on such studies offers an opportunity to provide ASCVD risk reduction information in a considerably larger number of appropriately-selected patients.

We made an empiric observation at our university medical center that incidental CAC was rarely reported on non-contrast non-gated chest CT studies. Based on this observation, we undertook a project to evaluate and address the routine reporting of incidental CAC on such studies.