Calculation of LDL LDL ‐Cholesterol vs. Direct Homogenous Assay

摘要

Background Low‐density lipoprotein cholesterol ( LDL c) can be calculated or measured directly and their accordance is the subject of controversy. Objectives The aim of this study was to identify the independent predictors of LDL c, to formulate the best equation for calculating LDL c and to evaluate the validity of it and the published formulas, including the new method with adjustable coefficient. Methods The profile of serum lipids and (apo)lipoproteins of 310 subjects was used to determine the most accurate formula for calculating serum LDL c. Serum lipids, lipoproteins and apolipoproteins were measured by enzymatic, new homogenous and immunoturbidometric methods, respectively. Results Multiple linear regression analysis indicates that total cholesterol, apoB, HDL c and triglyceride are independent predictors of LDL c. We proposed four new formulas to calculate LDL c. As total cholesterol ( TC ) is the major determinant of LDL c, it can be estimated simply as 0.545 of total cholesterol. Inclusion of HDL c, triglyceride, apoB and a constant value improved the equation slightly. The equation of: LDL c (mg/dl) = 0.75 TC ? 0.5 HDLc ? 0.1 TG had the lowest mean and SD of difference among all the methods examined here. LDL c was also calculated by the new modified Friedewald's equation using adjustable factor from Martin's table, but it did not improve the results significantly. LDL c gap was correlated significantly and positively with triglyceride and negatively with cholesterol or its subfractions. Conclusions Our data suggest the simplest formula: LDL c = 0.545 TC or a more detailed: LDL c = 0.75 TC ? 0.5 HDLc ? 0.1 TG be used for calculating serum LDL c.