The clinical significance of serum high density lipoproteins.

Serum high density lipoproteins (HDL) are a protective factor against atherosclerosis. Many epidemiological studies show a strong inverse relationship between serum HDL-cholesterol (HDL-C) and the likelihood of developing coronary artery disease (CAD). HDL-C levels appear to be a stronger predictive factor for CAD than serum total or low density lipoprotein cholesterol (LDL-C) levels. In the presence of high HDL-C levels, the development of CAD is unlikely even in persons with increased total or LDL-C. Conversely, subjects with low serum levels of HDL-C are at increased risk even if their total and LDL-C is within the "desirable" range. A number of studies have also shown that increasing HDL-C levels is associated with both primary and secondary prevention of atherosclerosis. HDL-C levels should be estimated in individuals with family and/or personal history of premature atherosclerosis, even if they have normal total cholesterol. Only the current problems with the accuracy and precision of the serum HDL-C assay prevent it from being the single most important test for assessment of the lipid risk factors for CAD. The most frequent causes of low HDL-C are smoking, obesity, and hypertriglyceridemia. Treatment of low HDL-C includes removal of these factors, and if this is ineffective, use of drugs. Gemfibrozil and niacin are most effective in raising serum HDL-C, although a number of other medications can markedly improve the total:HDL-C ratio.