A rapid and sensitive micro-assay for the enzymatic determination of plasma and lipoprotein cholesterol.

A rapid and inexpensive micro-assay for determining cholesterol in plasma and isolated lipoprotein fractions has been established which utilizes a commercially available enzymatic reagent with semi-automated instruments and microtiter plates. The assay is sensitive, precise, and easy to perform. The color development is linear from 0.4 to 20 micrograms cholesterol/well, with sample volumes of 2 to 100 microliters. Inter- and intra-assay variability yielded coefficients of variation (CV) of 2.75% (n = 51) and 1.09% (n = 32), respectively. The concentrations of total plasma and lipoprotein cholesterol (d greater than 1.006 g/ml) obtained with this method were compared with those analyzed in a lipid laboratory standardized to the Centers for Disease Control. The correlation coefficients between the two methods were 0.976 and 0.964, respectively. For total high density lipoprotein (HDL) and the HDL3 subfraction, inter-assay variability was 4.12% and 6.33% (n = 27), respectively; the intra-assay variability was 2.79% and 4.19% (n = 12).