Young Adult CAC Scans May Be More Fruitful for These Groups

Clinicians can gain a fuller picture of subclinical atherosclerosis in young people thanks to a new tool that calculates coronary artery calcium (CAC) percentile scores by age, sex, and race.

For people ages 30-45 years without known atherosclerotic cardiovascular disease (ASCVD), the prevalence of any CAC (CAC >0) was 21%, according to an analysis of nearly 20,000 people who had CAC scanning as part of the CARDIA study, the CAC Consortium, or the Walter Reed Cohort.

CAC was observed in 26% of white men, 16% of Black men, 10% of white women, and 7% of Black women. A non-zero score put the following groups in the 90th percentile of CAC:

• All women across the cohort
• White men at age 34 years
• Black men at age 37 years

A manuscript describing the online CAC percentile calculator was published by Michael Blaha, MD, MPH, of Johns Hopkins University School of Medicine in Baltimore, and colleagues in the May 17 issue of the Journal of the American College of Cardiology.

“Our results lay the groundwork for the development of future guidelines for targeted measurement, reclassification of long-term risk, and potential recommendations for intensive preventive therapy among select young adults,” Blaha’s group wrote.

CAC scanning provides an opportunity for early detection of subclinical atherosclerosis to help direct primary prevention therapies. CAC scoring had already been validated for ASCVD risk stratification in middle- and older-age adults. The existing MESA CAC Reference tool is limited to ages 45-84 years, however.

Given the “rising interest to predict the conversion to CAC >0 to determine when an individual should have their first CAC examination,” the authors suggested that the CAC probabilities they found for 30- to 45-year-olds “may aid the identification of cutoffs for targeted scanning of select young adult populations.”

Nevertheless, the study did not link CAC scores to long-term clinical outcomes.

More work is needed to assess whether CAC screening in young adults improves adherence to preventive recommendations and ultimately affects clinical outcomes, according to an accompanying editorial by Gregory Thomas, MD, MPH, of MemorialCare Heart & Vascular Institute in Fountain Valley, California, and Nathan Wong, PhD, of the University of California Irvine.

The editorialists did not endorse universal screening for CAC in young adults, instead identifying certain groups at higher risk, such as people with familial hypercholesterolemia or a family history of premature ASCVD, who may benefit from CAC screening.

For now, it is unclear how the calculator from Blaha and colleagues can be applied in current practice.

Current American cholesterol guidelines recommend “consideration of CAC scores to further inform treatment decisions beyond risk-scoring and risk-enhancing factors,” Thomas and Wong wrote.

“This recommendation, however, is based primarily on adults aged ≥45 years in MESA in which a CAC score of >100 identified those with a favorable net clinical benefit for statin use. Such an analysis is not available for younger adults, nor is the guideline recommended Pooled Cohort Equation score for 10-year ASCVD risk calculation applicable to those aged <40 years,” they cautioned.

The study from Blaha’s group included 19,725 asymptomatic individuals (mean age 41, 27.4% women) from the three aforementioned studies.

Major limitations of the analysis included samples that were too small to generate CAC probabilities for races and ethnicities beyond Black and white groups. Also, generalizability was questionable given that some participants had been referred for CAC scanning for clinical indications.

Nevertheless, the CAC percentiles generated by the investigators followed the patterns observed in the older MESA cohort. At age 45 years, where the present percentile estimates end and MESA estimates begin, the prevalence estimates of CAC >0 were similar between cohorts, according to Blaha and colleagues.