Enzymatic determination of lipoprotein-X, a specific serum cholestasis marker.

Non-esterified cholesterol was determined enzymatically with the cholesterol oxidase-peroxidase reaction using phenol and 4-aminophenazone as chromogens. This assay as done in the supernatant containing the lipoprotein-X. Other serum lipoproteins were removed by precipitation with heparin and zinc acetate followed by centrifugation. No standardization was required, the lipoprotein-X concentration being calculated with the use of the constant.