Comparison of LDL-cholesterol estimate using the Friedewald formula and the newly proposed de Cordova formula with a directly measured LDL-cholesterol in a healthy South African population

Abstract

Background: The accurate determination of low density lipoprotein cholesterol (LDL-c) is pertinent in clinical practice. Most laboratories employ the Friedewald formula, for convenient estimation of LDL-c, despite its shortfalls. Different formulae have been proposed for use, for more accurate but convenient estimation of LDL-c. Here, we compare a new formula recently proposed by de Cordova et al., with that of Friedewald and LDL-c determined by a homogeneous assay. We also assess its performance at very low TG levels against the modified Friedewald formula recommended by Ahmadi et al. Methods: A database of 587 adults from the 'Establishing Reference Intervals for Selected Analytes in South Africa' study was utilized. Fasting samples were assayed for lipids. LDL-c was determined by the Daiichi method. Performance of the Friedewald and the de Cordova formulae was compared. This was exclusively repeated at very low TG levels (<1.13 mmol/L), this time, including the Ahmadi formula. Results: The Friedewald formula and the de Cordova formula both had high correlations with the direct LDL-c (r ¼ 0.98 and r ¼ 0.97, respectively), although the latter showed an inconsistent bias at different LDL-c levels. The two formulae had a higher correlation (r ¼ 0.98) than the Ahmadi formula (r ¼ 0.92) at very low TG levels. Conclusions: The Friedewald formula showed better agreement with the direct LDL-c than the de Cordova formula, at various LDL-c levels, in our population. It also performed better than the Ahmadi formula at very low TG levels. We therefore advise that it remains the formula of choice for LDL-c estimation in South Africa.

Comparison of equations for the calculation of LDL-cholesterol in hospitalized patients

“…bias the lower the LDL-C level using the de Cordova formula, as shown in their study [24]. The other three formulae showed a more uniform distribution of points with the Bland-Altman plots, making the bias observed with these formulae more predictable than the de Cordova formula.…”

“…The de Cordova formula is the most recently published formula and reports better accuracy than the Friedewald in calculating LDL-C [23]. However, a subsequent analysis of 597 healthy subjects showed better agreement of the Friedewald formula with a directly measured LDL-C [24]. Another recent study compared four formulae in 164 subjects including those with dyslipidemias and co-morbidities and found that the Friedewald equation had the best overall performance for calculating LDL-C [33].…”

“…Secondly, although we used a non-reference method for the measurement of LDL-C, as with two similar previous analyses [23,24], our methods meet the NCEP standards of precision. Although we were unable to evaluate the formulae by disease categories,…”

“…However, this formula also showed bias at low levels of LDL-C in a subsequent study of 576 healthy subjects in South Africa [24].…”

Calculated Low Density Lipoprotein-Cholesterol: Friedewald's Formula versus Other Modified Formulas

“…However, the authors have suggested validating this formula in other populations. Onyenekwu et al [17] found that Friedewald formula showed better agreement with direct LDLc than the Cordova formula in healthy South African population.…”