Plasma lipid concentrations: the concept of "normality" and its implications for detection of high cardiovascular risk.

The relation between serum cholesterol concentrations and the incidence of coronary heart disease is continuous and curvilinear; there is neither epidemiological nor biological evidence to support the existence of a threshold value. There is a clinical need, however, for an acceptable definition of action limits and desirable ranges, based on the evidence that raised cholesterol concentrations are causally related to atherosclerotic heart disease. The European Atherosclerosis Society has proposed a set of cut off points, which, together with age and the presence of other risk factors, direct the clinician to an appropriate level of treatment. Because the changes of serum cholesterol during adult life appear unphysiological, these action limits do not require adjustment for age. The distribution of serum cholesterol in the United Kingdom population is such that a case finding strategy is required to identify the many persons at very high risk of coronary disease. Measurements of triglyceride, high density lipoprotein, apolipoproteins, and the investigation of hyperlipoproteinemia are informative but less mandatory.