Limitations of Direct Methods and the Reference Method for Measuring HDL and LDL Cholesterol

Abstract

To the Editor: Miller and colleagues (1) compared the results obtained by direct measurements of HDL cholesterol (HDL-C) and LDL-C with those obtained with reference methods requiring ultracentrifugation. They used frozen pooled serum samples and fresh serum samples from 37 healthy controls and 138 individuals with dyslipidemia or heart disease that they had obtained from the NIH. Assay kits, calibrators, and controls were provided by 7 manufacturers. The authors reported CVs of <3.7% for HDL-C and <4.4% for LDL-C for the frozen serum pools, biases for fresh serum from the healthy controls of −5.4% to 4.4% for HDL-C and −6.8% to 1.1% for LDL-C. The biases for the patients with disease were −8.6% to 8.8% for HDL-C and −11.8% to 4.1% for LDL-C, compared with the reference method. The total error for the healthy controls ranged from −13.4% to 1.6% for HDL-C and from −13.3% to 13.5% for LDL-C. For the disease group, total errors ranged from −19.8% to 36.3% for HDL-C and from −26.6% to 31.9% for LDL-C. The authors concluded that 6 of 8 direct HDL-C …