Continuous-flow enzymic determination of serum total and high density lipoprotein cholesterol using microlitre sample volumes.

We determine serum total cholesterol and high-density lipoprotein cholesterol (HDL-C) using a modified Technicon Auto Analyzer II-BMC enzymic system. The method uses 25 microL of sample (serum or supernate) for cholesterol determinations. Pooled serum which was calibrated indirectly against CDC's Abell-Kendall method was used for standardization. Accuracy and precision for total cholesterol determinations are comparable to those obtained using a modified Technicon AAII method. Coefficients of variation for the determination of HDL-C prepared by heparin/Mn++ precipitation are 6.4% and 4.6% at concentration levels of 0.70 mmol/L and 0.94 mmol/L respectively. The interchangeable use of deionized-distilled water and 0.15 mol/L NaCl solution for dilution of samples analyzed by the micro method is shown to produce significantly different cholesterol estimates. The reduced reagent volumes significantly lower the cost of cholesterol determinations. The system is simple, inexpensive and yields reliable cholesterol and HDL-C results.