How much does HDL cholesterol add to risk estimation? A report from the SCORE Investigators.

Background: Systematic COronary Risk Evaluation (SCORE), the risk estimation system recommended by the European guidelines on cardiovascular disease prevention, estimates 10-year risk of cardiovascular disease mortality based on age, sex, country of origin, systolic blood pressure, smoking status and either total cholesterol (TC) or TC/high-density lipoprotein cholesterol (HDL-C) ratio. As, counterintuitively, these two systems perform very similarly, we have investigated whether incorporating HDL-C and TC as separate variables improves risk estimation.

Methods: The study consisted of 57,302 men and 47,659 women. Cox proportional hazards method was used to derive the function including HDL-C and an identical function without HDL-C for comparison. Risk charts were developed to illustrate the results.

Results: Inclusion of HDL-C resulted in a modest but statistically significant improvement in risk estimation, based on the area under receiver operating characteristic curve (AUROC); 0.814 versus 0.808, P value less than 0.0001, for the functions with and without HDL-C, respectively. Addition of HDL-C also resulted in a significant and important improvement in risk estimation as measured by net reclassification index, which is highly clinically relevant. Improvement in risk estimation was greatest in women from high-risk countries, in terms of both AUROC and net reclassification index.

Conclusion: For the general population, the inclusion of HDL-C in risk estimation results in only a modest improvement in overall risk estimation based on AUROC. However, when using the more clinically that examines reclassification of individuals, clinically useful improvements occur. Inclusion of HDL may be particularly useful in women from high-risk countries and individuals with unusually high or low HDL-C levels. Addition of HDL-C is particularly applicable to electronic, interactive risk estimation systems such as HeartScore.