Predictive value of clinical risk assessment tools and guidelines for 10-year coronary heart disease risk in practice-based primary care

Summary Background: Risk for developing myocardial infarction derived from risk tables in primary care subjects in Switzerland may over- or un- derestimate risk. Coronary calcifications may improve the performance of risk tables. Methods: We used coronary calcium score percentiles >50 (CS% >50) as a surrogate marker for 10-year myocardial infarction risk in a prospective cross-sectional monocenter study. CS% >50 was compared to several risk charts, was used to reclassify subjects in the intermediate risk category assessed by Fram- ingham risk scores (FRS), and was used to cal- culate a cohort specific correction factor for FRS and PROCAM. Results from risk charts were entered into the Bayes formula as the pretest risk estimates. Subjects in our cohort were 100 primary care patients with no known history of cardiovascular disease randomly selected from three primary care practices. Results: The sensitivity of FRS to detect CS% >50 was 47%, and specificity was 85%. NCEP III and Swiss guidelines had sensitivi- ties of 53% and 67%, respectively (p = ns), and specificities of 66% and 67% (p 50-derived post-test probabilities shifted 16 subjects (76%) into the low-risk cat- egory and 5 subjects (24%) into the high-risk category. Cohort-specific correction factors were 0.68 for FRS and 0.64 for PROCAM. Conclusions: For our Swiss German co- hort, FRS and PROCAM tended to overesti- mate risk. A biological risk marker (coronary calcifications) may allow improvement of risk prediction in primary care subjects with inter- mediate risk and also helps in the calculation of cohort-specific correction factors.