Comparison of Two Homogeneous LDL-Cholesterol Assays Using Fresh Hypertriglyceridemic Serum and Quantitative Ultracentrifugation Fractions

Aim: The purpose of this study was to compare two homogeneous assays of low-density lipoprotein-cholesterol (LDL-C) with a modified beta quantification reference measurement for LDL-C (BQ-LDL), fractions of chylomicron (CM), very low-density lipoprotein (VLDL) and intermediate-density lipoprotein (IDL) by quantitative ultracentrifugation in patients with hypertriglyceridemia. Methods: Two homogeneous LDL-C assays (LDL-C(K), Kyowa Medex and LDL-C(S), Sekisui Medical) were used to measure 198 samples of fresh anonymized leftover sera with hypertriglyceridemia (≥ 150 mg/dL). Of these, 32 samples with discrepant LDL-C levels or hypertriglyceridemia (≥ 400 mg/dL) were used for further analysis. Quantitative ultracentrifugation was used to separate samples. Results: The two homogeneous LDL-C assays had a strong correlation with each other for the samples from 198 patients with hypertriglyceridemia. LDL-C(K) and LDL-C(S) in 32 selected samples were strongly correlated with BQ-LDL. In both homogeneous assays, cholesterol in the CM and VLDL fractions was measured as part of the LDL-C. A weak correlation was found between cholesterol in the VLDL fraction and LDL-C using the two homogeneous assays, but no correlation was found with cholesterol in the CM fraction. Cholesterol in the IDL fraction was also measured as part of the LDL-C in both assays. Conclusion: Both homogeneous assays partially detected cholesterol in the chylomicron and VLDL fractions, but LDL-C measured by both homogeneous assays correlated with BQ-LDL.