Estimation of LDL cholesterol based on the Friedewald formula and on apo Blevels

Objectives: The plasma apolipoprotein B (apo B) concentrations have been co nsidered 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: 308-15). We undertook the present study to investigate the reliability of this formula in a large number of hyperlipidemic patients. Design and methods: 1) The Friedewald formula (LDL-F) and the apo B-based f ormula (LDL-B) were compared with the P-quantification reference procedure in 130 individuals with a wide range of total cholesterol CTC) and triglyce ride CTG) levels, and 2) the LDL-C levels obtained by the Friedewald formul a were compared with those calculated by the apo B-based formula in 1010 in dividuals attending our outpatient lipid clinic. Results: The LDL-F and the LDL-B formulae for LDL-C estimation were found t o be in good agreement with the beta -quantification (r = 0.96 and 0.97, re spectively). The bias of each method plotted as a function of TG (up to 4.5 2 mmol/L) was found positive for the LDL-F, whereas the LDL-B was independe nt of the concentrations of TG. When a large number of individuals were exa mined, a good correlation between the two equations was found (n = 1010, r = 0.98). The difference between the two methods was not correlated with ser um 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 To levels >2.26 mmol/L, although it undere stimates LDL-C concentrations. Furthermore, this equation can be used in hy pertriglyceridemic patients CTG >4.52 mmol/L) in whom the Friedewald equati on is inaccurate. Copyright (C) 2000 The Canadian Society of Clinical Chemi sts.