Comparative evaluation of the new Sheffield table and the modified joint British societies coronary risk prediction chart against a laboratory based risk score calculation

Abstract

Background: Management of borderline hypertension and hypercholesterolaemia is based on an individual's coronary heart disease (CHD) risk rather than arbitrary values for blood pressure or serum cholesterol. Prediction of CHD risk involves using tables, charts, or computer programs based on the Framingham equations. The new Sheffield table and modified joint British societies coronary risk prediction (JBS) chart are widely used. The JBS chart approximates age and systolic blood pressure, and the new Sheffield table dichotomises blood pressure, and these simplifications may lead to diagnostic inaccuracy. Methods: The diagnostic performance of the charts against an individualised laboratory based CHD risk calculation in 1102 subjects in primary care were evaluated and compared. Results: The new Sheffield table and modified JBS chart performed equally well with a respective diagnostic sensitivity and specificity of 91.6% (95% confidence interval 86.7% to 95.1%) and 93.8% (91.1% to 97.9%), and 93.6% (90.4% to 96.0%) and 94.7% (92.6% to 96.1%) at 10 year CHD risk of 15%; and of 95.2% (82.8% to 99.4%) and 97.9% (96.8% to 98.7%), and 90.5% (75.6% to 97.4%) and 100% (99.7% to 100%) at 10 year CHD risk of 30%. The modified JBS chart graphic display provides graded risk, which may be an advantage over the new Sheffield table, which identifies thresholds of risk. The new Sheffield table, unlike any other method, can be used as screening tool for cholesterol measurement. Conclusions: The new Sheffield table and modified JBS chart are valid for use in primary care since their diagnostic accuracy is unaffected by approximations in age and blood pressure. It is suggested that practitioners should choose whichever risk assessment tool they are comfortable with and use it.