Estimation of LDL cholesterol based on the Friedewald formula and on apo B levels.
OBJECTIVE
The plasma apolipoprotein B (apo B) concentrations have been considered to be a more accurate representation of atherogenic particles and it has been proposed that the formula LDL-C (mmol/L) = 0.41TC - 0.32TG + 1.70apo B - 0.27 is reliable for the estimation of LDL-C (Clin Chem 1997; 43: 808-15). We undertook the present study to investigate the reliability of this formula in a large number of hyperlipidemic patients.


METHODS
1) The Friedewald formula (LDL-F) and the apo B-based formula (LDL-B) were compared with the beta-quantification reference procedure in 130 individuals with a wide range of total cholesterol (TC) and triglyceride (TG) levels, and 2) the LDL-C levels obtained by the Friedewald formula were compared with those calculated by the apo B-based formula in 1010 individuals attending our outpatient lipid clinic.


RESULTS
The LDL-F and the LDL-B formulae for LDL-C estimation were found to be in good agreement with the beta-quantification (r = 0.96 and 0.97, respectively). The bias of each method plotted as a function of TG (up to 4.52 mmol/L) was found positive for the LDL-F, whereas the LDL-B was independent of the concentrations of TG. When a large number of individuals were examined, a good correlation between the two equations was found (n = 1010, r = 0.98). The difference between the two methods was not correlated with serum TG levels. However, it was correlated to serum TC, and apo B levels.


CONCLUSIONS
The LDL-B formula is a more reliable and accurate method than the LDL-F formula, especially at TG levels >2.26 mmol/L, although it underestimates LDL-C concentrations. Furthermore, this equation can be used in hypertriglyceridemic patients (TG >4.52 mmol/L) in whom the Friedewald equation is inaccurate.
Bairaktari
E
E
Laboratory of Biochemistry, University of Ioannina, Ioannina, Greece. ebairakt@cc.uoi.gr
Hatzidimou
K
K
Tzallas
C
C
Vini
M
M
Katsaraki
A
A
Tselepis
A
A
Elisaf
M
M
Tsolas
O
O
D001055:Apolipoproteins B / Q000097:blood*; D002624:Chemistry, Clinical / Q000379:methods*; D002784:Cholesterol / Q000097:blood; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood*; D016264:Dextran Sulfate / Q000494:pharmacology; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood / Q000175:diagnosis; D016014:Linear Models; D015636:Magnesium Chloride / Q000494:pharmacology; D014280:Triglycerides / Q000097:blood; D014461:Ultracentrifugation
D001055:Apolipoproteins B; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D014280:Triglycerides; D015636:Magnesium Chloride; D016264:Dextran Sulfate; D002784:Cholesterol