It is now generally accepted that hyperlipidemia must be interpreted in terms of hyperlipoproteinemia, for it is as lipoproteins that the major plasma lipids circulate, and any quantitative change in one or more of the lipids reflects a disturbance in the lipoproteins. This view underlies the re-examination of the hyperlipidemias lately undertaken in order to classify them in terms of lipoprotein alterations and has given rise to several alternative classifications, of which that from the National Institutes of Health has gained the widest acceptance. Within this study the subjects were classified according to the W.H.O. Classification; Table I is compatible with any system which reliably identifies and measures the individual lipoproteins and recognizes certain normal and abnormal variations. Plasma lipoproteins differ in their densities, flotation rates, electrophoretic mobility, relative content of triglycerides, cholesterol, and phospholipid and in the types and content of apo-protein. (Table II) Accordingly they may be separated by ultracentrifugation, precipitation or electrophoresis.peer-reviewe
