Validation of the Friedewald formula for the determination of low-density lipoprotein cholesterol compared with beta-quantification in a large population.
Lipoprotein data from 9477 subjects, covering a wide range of total plasma cholesterol levels, were used to examine the validity of the Friedewald formula for estimating plasma concentrations of low-density lipoprotein cholesterol (LDL-C) using high-density lipoprotein cholesterol (HDL-C) and triglyceride (TG) concentrations. Values of LDL-C obtained from the Friedewald formula were compared with values of LDL-C derived from preparative ultracentrifugation used as a reference method. We found that the bias associated with the Friedewald formula was not related to plasma LDL-C levels and was smaller than -4.0% even for plasma LDL-C values <3.0 mmol/l. Moreover, in the subgroup of individuals with plasma TG levels < or =4.5 mmol/l, the Friedewald formula underestimated LDL-C levels with a bias between -3.1% and -1.9% according to TG quartiles. Interestingly, the Friedewald formula showed no significant bias in patients with plasma TG levels between 4.51 and 8.82 mmol/l, suggesting that the calculated LDL-C are reliable and could be clinically useful in patients with plasma TG levels higher than 4.5 mmol/l which is the reference cut-point value used by most clinical laboratories. Finally, multiple regression analyses showed that the very low-density lipoprotein cholesterol (VLDL-C)/TG ratio represented nearly 63% (P < 0.0001) of the variance of the bias associated with the Friedewald formula. We concluded that the Friedewald formula may be reliable at low LDL-C levels and at TG levels up to 9 mmol/l but may be used with caution when the VLDL-C/TG ratio is high as observed in patients with type III dysbetalipoproteinemia.
Tremblay
André J
AJ
Lipid Research Center, CHUQ Research Center, Québec City, Qc, Canada.
Morrissette
Hugo
H
Gagné
Jean-Marc
JM
Bergeron
Jean
J
Gagné
Claude
C
Couture
Patrick
P
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002648:Child; D002675:Child, Preschool; D008078:Cholesterol, LDL / Q000097:blood*; D005260:Female; D006801:Humans; D006952:Hyperlipoproteinemia Type III / Q000097:blood*; D007223:Infant; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D014461:Ultracentrifugation / Q000379:methods
D008078:Cholesterol, LDL