Level 2 (mid-level) evidence
Accurate prediction of cardiovascular disease risk is crucial for the success of preventive measures. The American College of Cardiology/American Heart Association (ACC/AHA) 2013 guidelines recommend using race- and sex-specific Pooled Cohort Equations (PCE) to determine risk for atherosclerotic cardiovascular disease in patients aged 40 to 79 years. Treatment with high- or moderate-intensity statins is recommended for patients with a 10-year risk for atherosclerotic cardiovascular disease ≥7.5% on PCE. ACC/AHA guidelines also suggest considering other risk factors in those with PCE risk <7.5%, but this recommendation is limited by a lack of empiric evidence.
In a recent cohort study, 5,185 adults without baseline cardiovascular disease, statin use, or ankle brachial index ≥1.4 were evaluated to determine how PCE statin eligibility corresponded to observed cardiovascular events. The study evaluated 5 additional risk factors for cardiovascular disease: elevated coronary artery calcium score, myocardial infarction or stroke in first-degree relative, high-sensitivity C-reactive protein level ≥2 mg/dL, ankle brachial index <0.9; and low-density lipoprotein cholesterol level ≥160 mg/dL but <190 mg/dL. Atherosclerotic cardiovascular events, defined as myocardial infarction, coronary heart disease death, or fatal/nonfatal stroke, occurred in 6.2% of adults during the median 10.2-year follow-up. The event rate was 13.8% in the 1,000 adults with ≥7.5% risk and 4.7% in 4,185 adults with <7.5% PCE risk.
These additional risk factors were reassessed in the 3,882 adults in the study without diabetes and with an initial PCE risk <7.5% to more accurately determine the degree of risk for purposes of statin initiation. Overall, 11.1% were reclassified using at least 1 additional factor to ≥7.5% 10-year risk for atherosclerotic cardiovascular events, and according to the 2013 ACC/AHA guidelines, should receive statin therapy. Adults reclassified using coronary artery calcium level, family history, or high-sensitivity C-reactive protein had an observed 10-year cardiovascular event rate >10%, and were therefore at greater risk than the 7.5% threshold.
Three of the 5 additional risk factors examined identified patients originally classified as low risk who actually had a higher risk for cardiovascular events. The results of this study suggest that these equations may underestimate the risk for atherosclerotic cardiovascular events in some patients without diabetes who are classified as low risk. These results underscore that the PCE is not perfect. The PCE is a valuable risk assessment tool, but it should not be used blindly. The decision to initiate statin therapy requires individualized decision making, including consideration of additional factors that influence risk assessment.
Alan Ehrlich, MD, is a deputy editor for DynaMed, Ipswich, Mass., and assistant clinical professor in Family Medicine, University of Massachusetts Medical School in Worcester.
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