Serum Lipoprotein Composition in Different Types of Hyperlipoproteinemia

Abstract

At present the six types of hyperlipoproteinemia (HLP) defined in the WHO memorandum (1) as an extension of the typing system of Fredricks on et al (Z) is in common use. According to this memorandum the diagnosis of a type of HLP is based upon “elevation” of one or more of the following lipoprotein (LP) classes: chylomicrons, very low density LP (VLDL) and low density LP (LDL). This may seem simple and clear but there are many difficulties involved. One major problem is to define “elevated.” This definition may certainly vary depending on its purpose, which for example can be clinical (diagnostic, treatment), epidemiological, genetic, physiological, etc. The definition of “normal” and “elevated” may furthermore vary with factors such as age, sex, season, etc. Whatever the purpose is for definition of normal values we prefer to use the statistical method with construction of cumulative frequency curves for reasons discussed in detail elsewhere (3). With these curves it is easy to find the lipid level corresponding to a given percentile of the control (normal) population. In the study to be described we have for clinical purpose used the upper 90th percentile as an upper “normal” limit, values above are then considered elevated.