Clinical Information

Plasma lipoproteins are spherical particles containing varying amounts of cholesterol, triglycerides, phospholipids, and proteins. Phospholipids, free cholesterol, and proteins constitute the outer surface of the lipoprotein particle, while the inner core contains mostly esterified cholesterol and triglyceride in the blood stream. The relative proportions of the protein and the lipid determine the density of these lipoproteins and provide a basis on which to begin their classification. The classes are chylomicron, very-low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL). Numerous clinical studies have shown that the different classes have very distinct and varied effects on coronary heart disease risk.

The principle role of HDL cholesterol in lipid metabolism is the uptake and transport of cholesterol from peripheral tissues to the liver through a process known as reverse cholesterol transport (a proposed cardioprotective mechanism). Low HDL cholesterol levels are strongly associated with an increased risk of coronary heart disease.

The determination of serum HDL cholesterol is a useful tool in identifying high-risk patients. The Adult Treatment Panel of the National Cholesterol Education Program (NCEP) recommends that in all adults 20 years of age and over should obtain a fasting lipoprotein profile once every five years to screen for coronary heart disease.