Clinical efficacy of the direct assay method using polymers for serum high density lipoprotein cholesterol

The clinical efficacy and accuracy of the homogeneous assay method for the serum high density lipoprotein (HDL)-cholesterol determination were evaluated. The principle is as follows: low density lipoproteins (LDL) and very low density lipoproteins (VLDL) were coated by polymers and polyanion to be blocked from cholesterol esterase and cholesterol oxidase. The reaction of these enzymes for HDL cholesterol was enhanced with a detergent, and HDL cholesterol was selectively measured. Both within-run (n = 3, 20 times) and between-run (n = 3, 7 days) CVs were < 2%. The repeated freezing and thawing (4 times) of three distinct sera resulted in no changes of HDL cholesterol values. Additions of lipid emulsion (Triglyceride = 100 mg/dl) and free bilirubin (20 mg/dl) gave no effect. Linearity was found up to 300 mg/dl. Increases in HDL cholesterol values by the addition of VLDL (total cholesterol (TC) = 300 mg/dl) or LDL (TC = 300 mg/dl) to the tested sera were < 0.5%. The correlation coefficient of the new method with a precipitation method was 0.995 (n = 64). HDL-C values for patients with hyperlipidemia (Type IIa, IIb, or III, IV, and V) by this method were comparable with those obtained by the precipitation method. From these results, we concluded that the new method meets the requirements for accuracy, precision, ease of handling massive samples, and was clinically useful.