Underappreciated opportunities for high-density lipoprotein particles in risk stratification and potential targets of therapy.

The inverse relationship between high-density lipoprotein cholesterol (HDL-C) concentrations and coronary heart disease risk is well established. As a result, in recent years there have been significant resources focused on identifying therapies that raise HDL-C and ultimately reduce cardiovascular events. Unfortunately, a number of trials aimed at increasing HDL-C have failed to show improved outcomes, and hence, have cast doubt on the importance of HDL-C as a therapeutic target. HDL-C, however, is only one measure of HDL. HDL levels can also been estimated by quantifying apolipoprotein A-I (apoA-I) levels using enzyme immunoassay or by measuring HDL particle number (HDL-P) using nuclear magnetic resonance spectroscopy (NMR) or ion mobility. While these surrogate measures are correlated, they are not comparable. Lipoprotein-altering therapies have been shown to have different effects on HDL-C, apoA-I and HDL-P and several studies have demonstrated that HDL-P is a stronger predictor of coronary heart disease risk than HDL-C and/or apoA-I. This paper will review available evidence supporting the use of HDL-P as the biomarker of choice to assess the contribution of HDL to cardiovascular risk and as the primary goal of HDL-raising therapies.