[Quantitative determination of lipoprotein-X in blood serum].

Lipoprotein X is a reliable indicator of cholestasis. The present paper describes a simple method for direct measurement of lipoprotein X. Low-density lipoproteins, very low density lipoproteins, chylomicrons and abnormal lipoprotein X are precipitated from the serum by treatment with a solution of polyethylene glycol (PEG) MW 6000. Then phosphotungstic acid and PEG 6000 solution are added to the precipitate. The lipoprotein X is in the supernatant, where its level can be estimated from the content of phospholipids and cholesterol. This method permits the determination of lipoprotein X in several samples simultaneously, requires no sophisticated equipment, is sensitive, reproducible, accurate, and cheap.