Reporting Coronary Artery Calcium on Low-Dose Computed Tomography Impacts Statin Management in a Lung Cancer Screening Population
Background: Cigarette smoking is an independent risk factor for atherosclerotic cardiovascular disease (ASCVD). Concomitant use of low-dose computed tomography (LDCT) for coronary artery calcium (CAC) scoring with lung cancer screening (LCS) has been proposed to further determine ASCVD risk and mortality. We aimed to determine the validity of LDCT in identifying CAC and its impact on statin management.
Methods: We conducted a retrospective review from November 2020 to May 2021 of Military Health System (MHS) beneficiaries who received LCS with LDCT and were referred for CAC scoring with electrocardiogram-gated CT. Of the 190 participants initially identified, 170 met study eligibility. The Agatston method was used to score CAC on both scan types.
Results: Participants had a mean (SD) age of 62.1 (4.6) years and were 70.6% male. CAC was seen more on ECG-gated CT compared with LDCT (88% vs 74%, P < .001). The Spearman correlation and Kendall W coefficient of concordance of CAC scores between the 2 scan types was 0.945 ( P < .001) and 0.643, respectively. The κ statistic between CAC scores on the 2 different scans was 0.49 (SE κ = 0.048; 95% CI, -0.726-1.706), and the weighted κ statistic was 0.711. Bland-Altman analysis demonstrated a mean bias of 111.45 Agatston units, with limits of agreement between -268.64 and 491.54, suggesting CAC scores on electrocardiogram-gated CT were on average about 111 units higher than those on LDCT. There was a statistically significant proportion of nonstatin participants who met statin criteria based on additional CAC reporting ( P < .001).
Conclusions: CAC scores are highly correlated and concordant between LDCT and electrocardiogram-gated CT. Smokers undergoing annual LDCT may benefit from concomitant CAC scoring to help stratify ASCVD risk.
Limitations
Our study cohort was composed of MHS beneficiaries. Compared with the general population, these individuals may have greater access to care and be more likely to receive statins after preventive screenings. Additional studies may be required to assess CAC-associated statin eligibility among the general population. As discussed previously LDCT was not performed concomitantly with the ECG-gated CT. Although there was moderate to substantial CAC agreement between the 2 scan types, the timing difference could have led to absolute differences in CAC scores across both scan types and impacted the ability to detect low-level CAC on LDCT. CAC values should be interpreted based on the respective scan type.
Conclusions
LDCT is a reliable diagnostic alternative to ECG-gated CT in predicting CAC. CAC scores from LDCT are highly correlated and concordant with those from gated CT and can help guide statin management in individuals with intermediate ASCVD risk. The proposed duality of LDCT to assess ASCVD risk in addition to lung cancer can reduce the need for unnecessary scans while optimizing preventive clinical care. While coronary calcium and elevated CAC scores can facilitate clinical decision making to initiate statin therapy for intermediate-risk patients, physicians must still determine whether additional cardiac testing is warranted to avoid unnecessary procedures and health care costs. Smokers undergoing annual LDCT may benefit from standardized CAC scoring to help further stratify ASCVD risk while limiting the expense and radiation of additional scans.
Acknowledgments
The authors thank Ms. Lorie Gower for her contributions to the study.
