Lipid phenotypes may be changed by stress or changes in diet. Phenotyping is invalid in the presence of secondary disorders, such as diabetes, renal failure or nephritis. They are classified into four major categories.
Chylomicrons function primarily to transport dietary triglycerides from the intestines.
The cholesterol of atherosclerotic plaques is derived from LDLs and increases in LDLs are associated with an increased risk of coronary artery disease. HDLs play a key role in reverse cholesterol transport, in which there is an efflux of cholesterol from the peripheral cells to the liver where it is removed from the plasma. There is an inverse relationship between the level of plasma HDL cholesterol and the risk of heart disease. Patients may be phenotyped using Fredrickson's classification system. The relative amounts of triglycerides, cholesterol, and lipoproteins are considered in this system.