High Density Lipoprotein Assessment Revisited: A Review of Foundational Understanding and Recent Developments in Function, Particle Size, and Cardiometabolic Impact

High density lipoprotein (HDL) has historically been considered cardioprotective, with HDL cholesterol (HDL-C) levels widely used as a biomarker of cardiovascular disease risk. However, accumulating evidence suggests that HDL-C concentration alone does not adequately capture the complex biological functions of HDL particles. This review revisits the evolving understanding of HDL biology and examines the emerging importance of HDL functionality, particle size and particle number in cardiometabolic risk assessment. It further highlights recent methodological advances that enable more detailed characterization of HDL heterogeneity. Contemporary research demonstrates that HDL represents a structurally and functionally heterogenous group of particles with diverse biological activities. Cardioprotective effects attributed to HDL are increasingly linked to functional properties rather than to HDL-C levels alone. Growing evidence suggest that HDL particle concentration and subclass distribution may correlate more strongly with cardiovascular outcomes than conventional HDL-C measurements. Technological advances, such as nuclear magnetic resonance(NMR) spectroscopy and polyacrylamide gel electrophoresis based systems like the Lipoprint platform, now allow more precise quantification and classification of HDL subfractions. Current evidence challenges the traditional reliance on HDL-C as a surrogate marker of cardiovascular protection. Instead, HDL should be viewed as a dynamic and heterogenous lipoprotein system in which particle characteristics and functional capacity are critical determinants of cardiometabolic risk. Incorporating measurement of HDL particle distribution and functionality into research and clinical evaluation may improve cardiovascular risk stratification and deepen understanding of HDL biology. Continued advances in analytical technologies and functional assays are likely to reshape HDL assessment and support more precise, mechanism based approaches to cardiovascular disease prevention and management.