Editor—The paper by Nanchahal et al indicates that substantially fewer men and women without overt cardiovascular disease would be eligible for drug treatment if the standard 1991 Framingham risk equation for coronary heart disease risk that is used in the Joint British Cardiovascular Recommendations were to be replaced with the 2000 model.1,2
This would be an important finding for developers of cardiovascular guidelines and budget holders if the newer risk equation was substantially more accurate than the old one. This seems unlikely, however, because the new risk equation is based on a modest number of end points (224 for men and 108 for women), and the equation for men incorporates the same set of risk factors as the 1991 equation.
What guideline developers need is a comparison of the predictions of each risk equation with observed incident cardiovascular events, preferably over a range of thresholds (an analysis of the characteristics of receiver and operator). Published analyses of receiver-operator characteristics show that Framingham risk equations are only modestly accurate against observed events of coronary heart disease.3,4 We have also shown that the 1991 and 2000 risk equations have very similar discriminability for coronary heart disease events in a New Zealand cohort (unpublished data).
Fortunately for guideline developers, the interesting findings reported in this paper do not provide a good reason to abandon the 1991 Framingham risk equations in favour of the 2000 version. Cardiovascular guidelines will need to be revised when better risk equations become available.
References
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