Inaccuracies Revealed in Cardiovascular Risk Calculators

February 19, 2015
Michael R. Page, PharmD, RPh

The clinical risk calculators incorporated into dyslipidemia treatment guidelines may overestimate a patient's risk of experiencing a cardiovascular event.

Investigators at Johns Hopkins University claim that clinical risk calculators overestimate—and sometimes underestimate—a patient’s risk of experiencing a cardiovascular event over 10 years, which may affect the implementation of dyslipidemia treatment guidelines.

Cardiovascular risk calculators have recently become important in clinical practice, given their inclusion in both the American College of Cardiology (ACC)/American Heart Association (AHA) and National Lipid Association (NLA) treatment guidelines for dyslipidemia. With these calculators, the ACC/AHA and NLA guideline authors hoped to select candidates for lipid-lowering therapy based on several factors, rather than simply treating to a target low-density lipoprotein cholesterol (LDL-C) concentration.

However, the guidelines already diverge on which risk calculators to use. While the NLA treatment guidelines rely on risk factors determined by the Framingham Heart Study, the ACC/AHA guidelines calculate risk based on the Pooled Cohort Equations.

In a study published in the Annals of Internal Medicine on February 17, 2015, Andrew P. DeFilippis, MD, MSc, and colleagues compared the risk predicted by clinical calculators with the actual risk of developing atherosclerotic cardiovascular disease (ASCVD) after approximately 10 years among patients enrolled in the MultiEthnic Study of Atherosclerosis (MESA).

Importantly, the MESA study population was more ethnically diverse than those studied to generate the Pooled Risk Equations (African Americans and non-Hispanic white men and women) and the Framingham Heart Study (residents of Framingham, Massachusetts). Unlike those populations, the MESA study included patients from a variety of ethnic groups.

A total of 4227 patients without diabetes who were aged between 50 and 74 years participated in the MESA study. Investigators compared cardiovascular outcomes after 10.2 years of follow-up with the patients’ predicted risk using the Pooled Risk Equations, Framingham Risk Score, and Reynolds Risk Score.

The Framingham and Pooled Risk Equations overestimated cardiovascular risk in men by 37% to 154%. Results were slightly better in women, but cardiovascular risk was still overestimated by 8% to 67%.

The Reynolds Risk Score overestimated cardiovascular risk in men by 9%, but underestimated risk in women by 21%.

In a press release, study author Michael Blaha, MD, MPH, director of clinical research at the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease, stated, “Our results reveal a lack of predictive accuracy in risk calculators and highlight an urgent need to reexamine and fine-tune our existing risk assessment techniques.”

Although more research will be necessary to validate clinical calculators, particularly in multiethnic populations, it is important to consider multiple factors in the deciding whether or not to initiate treatment with statins in a given patient. With the results of this study, it may be possible to fine-tune treatment guidelines to accurately predict the risk of cardiovascular events among ethnically diverse patients.

References

1. DeFilippis AP, Young R, Carrubba CJ, et al. An analysis of calibration and discrimination among multiple cardiovascular risk scores in a modern multiethnic cohort. Ann Intern Med. 2015;162(4):266-275.

2. Stone NJ, Robinson JG, Lichtenstein AH, et al. Treatment of blood cholesterol to reduce atherosclerotic cardiovascular disease risk in adults: synopsis of the 2013 American College of Cardiology/American Heart Association cholesterol guideline. Ann Intern Med. 2014;160(5):339-343.

3. Jacobson TA, Ito MK, Maki KC, et al. National Lipid Association recommendations for patient-centered management of dyslipidemia: part 1 - executive summary. J Clin Lipidol. 2014;8(5):473-488.