Calculation of LDL-Cholesterol vs. Direct Homogenous Assay.
BACKGROUND
Low-density lipoprotein cholesterol (LDLc) can be calculated or measured directly and their accordance is the subject of controversy.


OBJECTIVE
The aim of this study was to identify the independent predictors of LDLc, to formulate the best equation for calculating LDLc 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 LDLc. 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, HDLc and triglyceride are independent predictors of LDLc. We proposed four new formulas to calculate LDLc. As total cholesterol (TC) is the major determinant of LDLc, it can be estimated simply as 0.545 of total cholesterol. Inclusion of HDLc, triglyceride, apoB and a constant value improved the equation slightly. The equation of: LDLc (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. LDLc 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. LDLc gap was correlated significantly and positively with triglyceride and negatively with cholesterol or its subfractions.


CONCLUSIONS
Our data suggest the simplest formula: LDLc = 0.545 TC or a more detailed: LDLc = 0.75 TC - 0.5 HDLc - 0.1 TG be used for calculating serum LDLc.
Department of Clinical Biochemistry and Immunogenetic Research Center, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Mazandaran, Iran.
Mehdi
M
Rasouli
Department of Clinical Biochemistry and Immunogenetic Research Center, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Mazandaran, Iran.
Hossein
H
Mokhtari
D000368:Aged; D001055:Apolipoproteins B / Q000097:blood; D001774:Blood Chemical Analysis / Q000379:methods*; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis
D001055:Apolipoproteins B; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL
ApoB; HDLc; LDLc; cholesterol; homogenous assay