Seven Direct Methods for Measuring HDL and LDL Cholesterol Compared with Ultracentrifugation Reference Measurement Procedures

distributor for directly measuringHDL cholesterol (C) and LDL-C were evaluated for imprecision, trueness, total error, and specificity in nonfrozen serum samples. METHODS: We performed each direct method accord-ing to the manufacturer’s instructions, using a Roche/ Hitachi 917 analyzer, and compared the results with those obtained with reference measurement proce-dures for HDL-C and LDL-C. Imprecision was esti-mated for 35 runs performedwith frozen pooled serum specimens and triplicate measurements on each indi-vidual sample. Sera from 37 individuals without dis-ease and 138 with disease (primarily dyslipidemic and cardiovascular) were measured by each method. True-ness and total error were evaluated from the difference between the direct methods and reference measure-ment procedures. Specificity was evaluated from the dispersion in differences observed. RESULTS: Imprecision data based on 4 frozen serum pools showed total CVs3.7 % forHDL-C and4.4% for LDL-C. Bias for the nondiseased group ranged from 5.4 % to 4.8 % for HDL-C and from 6.8 % to 1.1 % for LDL-C, and for the diseased group fro