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Validation of the atherosclerotic cardiovascular disease Pooled Cohort risk equations
Paul Muntner1, Lisandro D Colantonio2, Mary Cushman3
1Department of Epidemiology, University of Alabama at Birmingham2Department of Medicine, University of Alabama at Birmingham.
Insights
The ACC/AHA Pooled Cohort risk equations accurately estimate 5-year atherosclerotic cardiovascular disease (CVD) risk in US adults considered for statin therapy. These equations show good calibration and discrimination, supporting their use in clinical decision-making.
Area of Science:
- Cardiovascular Medicine
- Epidemiology
- Preventive Cardiology
Background:
- The American College of Cardiology/American Heart Association (ACC/AHA) Pooled Cohort risk equations are crucial for estimating atherosclerotic cardiovascular disease (CVD) risk.
- These equations guide decisions regarding statin initiation for primary prevention.
- Validation in contemporary US populations is essential to ensure their continued utility.
Purpose of the Study:
- To evaluate the calibration and discrimination of the ACC/AHA Pooled Cohort risk equations.
- To assess the accuracy of these risk equations in a contemporary US population.
- To determine the reliability of the equations for guiding statin initiation.
Main Methods:
- Analysis of 10,997 adults aged 45-79 from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study (2003-2010).
- Focus on participants without existing CVD or diabetes, with LDL-C 70-189 mg/dL, and not on statins.
- Comparison of predicted 5-year atherosclerotic CVD risk with observed adjudicated events (nonfatal MI, CHD death, stroke), including Medicare claims data for a subset.
Main Results:
- Observed and predicted 5-year atherosclerotic CVD incidence showed strong agreement across risk strata (<5%, 5-7.5%, 7.5-10%, ≥10%).
- The C-index for discrimination was 0.72 in the main cohort and 0.67 in the Medicare-linked subset.
- The Hosmer-Lemeshow test indicated good calibration in the Medicare-linked group (P=.71).
Conclusions:
- The ACC/AHA Pooled Cohort risk equations demonstrate good calibration and moderate-to-good discrimination in a contemporary US population.
- The findings support the continued use of these equations for assessing atherosclerotic CVD risk and informing statin therapy decisions.
- The study validates the reliability of the risk equations in the target population for whom they are intended.
Importance:
The American College of Cardiology/American Heart Association (ACC/AHA) Pooled Cohort risk equations were developed to estimate atherosclerotic cardiovascular disease (CVD) risk and guide statin initiation.
Objective:
To assess calibration and discrimination of the Pooled Cohort risk equations in a contemporary US population.
Design, Setting, And Participants:
Adults aged 45 to 79 years enrolled in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study between January 2003 and October 2007 and followed up through December 2010. We studied participants for whom atherosclerotic CVD risk may trigger a discussion of statin initiation (those without clinical atherosclerotic CVD or diabetes, low-density lipoprotein cholesterol level between 70 and 189 mg/dL, and not taking statins; n = 10,997).
Main Outcomes And Measures:
Predicted risk and observed adjudicated atherosclerotic CVD incidence (nonfatal myocardial infarction, coronary heart disease [CHD] death, nonfatal or fatal stroke) at 5 years because REGARDS participants have not been followed up for 10 years. Additional analyses, limited to Medicare beneficiaries (n = 3333), added atherosclerotic CVD events identified in Medicare claims data.
Results:
There were 338 adjudicated events (192 CHD events, 146 strokes). The observed and predicted 5-year atherosclerotic CVD incidence per 1000 person-years for participants with a 10-year predicted atherosclerotic CVD risk of less than 5% was 1.9 (95% CI, 1.3-2.7) and 1.9, respectively, risk of 5% to less than 7.5% was 4.8 (95% CI, 3.4-6.7) and 4.8, risk of 7.5% to less than 10% was 6.1 (95% CI, 4.4-8.6) and 6.9, and risk of 10% or greater was 12.0 (95% CI, 10.6-13.6) and 15.1 (Hosmer-Lemeshow χ2 = 19.9, P = .01). The C index was 0.72 (95% CI, 0.70-0.75). There were 234 atherosclerotic CVD events (120 CHD events, 114 strokes) among Medicare-linked participants and the observed and predicted 5-year atherosclerotic CVD incidence per 1000 person-years for participants with a predicted risk of less than 7.5% was 5.3 (95% CI, 2.8-10.1) and 4.0, respectively, risk of 7.5% to less than 10% was 7.9 (95% CI, 4.6-13.5) and 6.4, and risk of 10% or greater was 17.4 (95% CI, 15.3-19.8) and 16.4 (Hosmer-Lemeshow χ2 = 5.4, P = .71). The C index was 0.67 (95% CI, 0.64-0.71).
Conclusions And Relevance:
In this cohort of US adults for whom statin initiation is considered based on the ACC/AHA Pooled Cohort risk equations, observed and predicted 5-year atherosclerotic CVD risks were similar, indicating that these risk equations were well calibrated in the population for which they were designed to be used, and demonstrated moderate to good discrimination.
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