Differential reactivities of four homogeneous assays for LDL-cholesterol in serum to intermediate-density lipoproteins and small dense LDL: comparisons with the Friedewald equation.
BACKGROUND
In routine clinical laboratory testing and numerous epidemiological studies, LDL-cholesterol (LDL-C) has been estimated commonly using the Friedewald equation. We investigated the relationship between the Friedewald equation and 4 homogeneous assays for LDL-C.


METHODS
LDL-C was determined by 4 homogeneous assays [liquid selective detergent method: LDL-C (L), selective solubilization method: LDL-C (S), elimination method: LDL-C (E), and enzyme selective protecting method: LDL-C (P)]. Samples with discrepancies between the Friedewald equation and the 4 homogeneous assays for LDL-C were subjected to polyacrylamide gel electrophoresis and the beta-quantification method.


RESULTS
The correlations between the Friedewald equation and the 4 homogeneous LDL-C assays were as follows: LDL-C (L) (r=0.962), LDL-C (S) (r=0.986), LDL-C (E) (r=0.946) and LDL-C (P) (r=0.963). Discrepancies were observed in sera from type III hyperlipoproteinemia patients and in sera containing large amounts of midband and small dense LDL on polyacrylamide gel electrophoresis. LDL-C (S) was most strongly correlated with the beta-quantification method even in sera from patients with type III hyperlipoproteinemia.


CONCLUSIONS
Of the 4 homogeneous assays for LDL-C, LDL-C (S) exhibited the closest correlation with the Friedewald equation and the beta-quantification method, thus reflecting the current clinical databases for coronary heart disease.
Yamashita
Shizuya
S
Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. shizu@imed2.med.osaka-u.ac.jp
Kawase
Ryota
R
Nakaoka
Hajime
H
Nakatani
Kazuhiro
K
Inagaki
Miwako
M
Yuasa-Kawase
Miyako
M
Tsubakio-Yamamoto
Kazumi
K
Sandoval
Jose C
JC
Masuda
Daisaku
D
Ohama
Tohru
T
Nakagawa-Toyama
Yumiko
Y
Matsuyama
Akifumi
A
Nishida
Makoto
M
Ishigami
Masato
M
D000328:Adult; D000368:Aged; D008078:Cholesterol, LDL / Q000097:blood; D019411:Clinical Laboratory Techniques / Q000592:standards*; D003327:Coronary Disease / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000097:blood; D006801:Humans; D006952:Hyperlipoproteinemia Type III / Q000097:blood; D008074:Lipoproteins / Q000097:blood*; D053419:Lipoproteins, IDL / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood; D008875:Middle Aged; D008962:Models, Theoretical
D008078:Cholesterol, LDL; D008074:Lipoproteins; D053419:Lipoproteins, IDL; D008077:Lipoproteins, LDL