FROM ACC 17
A new study suggests calcium scores may help physicians as they navigate a wide cardiac screening guideline gap over recommendations about statin therapy in African Americans.
In a study sample of Mississippi residents, researchers found that the 2016 U.S. Preventive Services Task Force guidelines would reject statins for a quarter of the African Americans who’d be deemed statin eligible by the 2013 American College of Cardiology/American Heart Association (ACC/AHA) recommendations.
“ACC/AHA guidelines are more sensitive, but may lead to overtreatment of those who may not be at increased risk of cardiovascular disease,” said study coauthor Aferdita Spahillari, MD, a cardiology fellow at Tufts Medical Center and Beth Israel Deaconess Medical Center, Boston. In contrast, the task force guidelines “are more specific, yet they may miss individuals at higher risk who should be treated with statins,” she said.
Regardless of which screening guidelines are used, Dr. Spahillari said, “calcium scoring may aid decision making in those cases where guideline recommendations may be divergent.”
The study was presented at the annual meeting of the American College of Cardiology and published simultaneously in the JAMA Cardiology (doi: 10.1001/jamacardio.2017.0944).
The researchers sought to answer these questions: How do the ACC/AHA and task force guidelines perform at identifying at-risk African Americans? And can calcium scores help refine decisions regarding statins? According to Dr. Spahillari, the latter issue has been studied in whites but not large African American populations.
Insight could help physicians better provide preventive treatment to African Americans, who face a higher risk of cardiac problems compared with whites. In addition, “studies have shown that racial disparities exist in prescription of cardioprotective medications,” Dr. Spahillari said, “and African Americans are prescribed statins less frequently than whites.”
For the new study, researchers tracked 2,812 African American individuals aged 40-75 years (mean age 55 [SD 9.4], 65.3% female, mean body mass index 31.6 kg/m2 [SD 7.0]) in the Jackson, Miss., area. They were examined in 2000-2004, 2005-2008, and 2009-2013 and included if they didn’t show signs of prevalent subclinical and clinical atherosclerotic cardiovascular disease and weren’t on statins at baseline.
If the task force guidelines regarding 10-year risk had been in existence, 1,072 (38.1%) of the participants would have been deemed eligible for treatment. A higher number – 1,404 (49.9%) – would have been eligible under ACC/AHA guidelines (risk difference, 11.8%; 95% CI, 10.5-13.1; P less than .001).
The two sets of guidelines diverged on the eligibility of 13.8% of the total subjects: 361 (12.8%) were deemed eligible for statins by the ACC/AHA guidelines alone. (They account for 25.7% of all the statin-eligible subjects under the ACC/AHA guidelines.)
In contrast, the task force guidelines alone deemed 29 (1%) to be eligible.
Those deemed eligible for statins under both guidelines had a cardiovascular event rate of 9.6 per 1,000 patient-years (95% CI, 7.8-11.8, P = .003) over a median 10-year follow-up. The event rate for those only statin-eligible under the ACC/AHA guidelines had an event rate of 4.1 events per 1,000 patient-years (95% CI, 2.4-6.9; P = .003), which Dr. Spahillari calls “a low to intermediate rate suggesting a decreased sensitivity of the task force recommendations in identifying participants at risk of atherosclerotic cardiovascular disease.”
And what about CAC levels? Task force guidelines identified 404 of 732 (55.2%) African Americans with coronary calcium; ACC/AHA guidelines identified 507 (69.3%).
“Participants eligible for statins under the ACC/AHA guidelines who had CAC were at higher risk than those without CAC,” Dr. Spahillari said. Specifically, among those deemed eligible for statins by the ACC/AHA recommendations, the 10-year event rate per 1,000 person-years was 8.1 (95% CI, 5.9-11.1) in those with CAC and 3.1 (95% CI, 1.6-5.9) in those without CAC (P = .02).
The situation was different under the task force guidelines. CAC didn’t significantly affect the risk in those deemed eligible for statins by the task force guidelines, but it did seem to boost risk in those who weren’t statin eligible, she said.
Among those deemed not statin eligible by the task force guidelines, the event rate per 1,000 person-years was 2.8 in those with CAC (95% CI, 1.5-5.4) and 0.8 in those without (95%, CI 0.3-1.7) (P = .03).
How could CAC levels be useful for physicians? “As the role of CAC measurement is evolving, our findings support that measurement of CAC in an African-American population with an intermediate risk score would be clinically useful,” Dr. Spahillari said.
When ACC/AHA guidelines are used, she said, “the absence of CAC may reduce the number of individuals indicated for treatment with statins by ACC/AHA recommendations and temper concerns for overtreatment.”
What if a physician uses the task force guidelines in this population? “The presence of CAC may push a recommendation for statin treatment in individuals who would otherwise not be indicated for statins,” she said.
The National Heart, Lung, and Blood Institute and the National Institute on Minority Health and Health Disparities funded the study. One author reported funding from a National Institutes of Health grant. The others had no disclosures.