The clinical decision to treat hypercholesterolemia is premised on an awareness of
patient risk, and cardiac risk prediction models offer a practical means of determining
such risk. However, these models are based on observational cohorts where estimates
of the treatment benefit are largely inferred. The West of Scotland Coronary Prevention
Study (WOSCOPS) provides an opportunity to develop a risk-benefit prediction model
from the actual observed primary event reduction seen in the trial. Five-year Cox
model risk estimates were derived from all WOSCOPS subjects (n = 6,595 men, aged 45
to 64 years old at baseline) using factors previously shown to be predictive of definite
fatal coronary heart disease or nonfatal myocardial infarction. Model risk factors
included age, diastolic blood pressure, total cholesterol/ high-density lipoprotein
ratio (TC/HDL), current smoking, diabetes, family history of fatal coronary heart
disease, nitrate use or angina, and treatment (placebo/ 40-mg pravastatin). All risk
factors were expressed as categorical variables to facilitate risk assessment. Risk
estimates were incorporated into a simple, hand-held slide rule or risk tool. Risk
estimates were identified for 5-year age bands (45 to 65 years), 4 categories of TC/HDL
ratio (<5.5, 5.5 to <6.5, 6.5 to <7.5, > or = 7.5), 2 levels of diastolic blood pressure
(<90, > or = 90 mm Hg), from 0 to 3 additional risk factors (current smoking, diabetes,
family history of premature fatal coronary heart disease, nitrate use or angina),
and pravastatin treatment. Five-year risk estimates ranged from 2% in very low-risk
subjects to 61% in the very high-risk subjects. Risk reduction due to pravastatin
treatment averaged 31%. Thus, the Cardiovascular Event Reduction Tool (CERT) is a
risk prediction model derived from the WOSCOPS trial. Its use will help physicians
identify patients who will benefit from cholesterol reduction.