Analysis of Low-Density Lipoprotein Cholesterol by Homogenous Assay in Comparison with Friedewald Formula

Hur, Mina; Kim, Chang Soo; Park, Min Jeong; Kwak, Insuk; Lee, Kyu Man

Abstract

BACKGROUND
Low-density lipoprotein cholesterol (LDL-C) is a major risk factor in atherogenesis and coronary heart disease as well as a primary target of lipid-lowering therapy. LDL-C concentration by direct homogenous assay was compared with that of the Friedewald formula, which is widely used in spite of its limitations. METHODS: Between February and March 2002, we analyzed total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and LDL-C levels in 1, 161 subjects (601 men and 560 women). They were classified according to cutpoints of the National Cholesterol Education Program Adult Treatment Panel III guidelines. The LDL-C results by direct method and the Friedewald formula were compared according to the TG levels and their medical decision values. RESULTS: Overall results of the direct method (Y) and the Friedewald formula (X) were highly correlated (Y=0.90X+13.62, r=0.9225). LDL-C by the Friedewald formula, however, showed a tendency of underestimation at higher TG levels. The results of the direct method were significantly different compared with those of the Friedewald formula when TG > or =200 mg/dL (P<0.05). Although the agreement between the two methods for LDL-C was within an acceptable range, it was relatively poor from near optimal to higher levels of LDL-C compared with optimal levels. CONCLUSIONS: The Friedewald formula is unsatisfactory for clinical purposes, because the levels of LDL-C are unreliable at the TG levels > or =200 mg/dL. Therefore, a direct determination method with better analytical performance is required. A fully automated homogenous assay seems to improve the determination of LDL-C, and may have a role in the diagnosis and management of hyperlipidemic patients.