Extreme concentrations of high density lipoprotein cholesterol affect the calculation of low density lipoprotein cholesterol in the Friedewald formula and other proposed formulas

ObjectivesTo investigate the effect of extreme levels of high density lipoprotein cholesterol (HDL-C) in the calculation of low density lipoprotein cholesterol (LDL-C) using Friedewald's formula (FF) and other formulas proposed recently.Design and methodsLipoprotein profile was performed in 2603 samples with HDL-C ≤ 20 mg/dL and 1953 samples with HDL-C ≥ 100 mg/dL.ResultsWilcoxon's and Student's t-tests showed significant differences (p < 0.001) between calculated LDL-C by different formulas and direct determination in the two groups of HDL-C values. Passing–Bablok regression and Bland–Altman plot showed disagreement for the four formulas studied, except for Vujovic formula in the HLD-C ≥ 100 mg/dL group.ConclusionsOur results suggested that none of the formulas under analysis should be used for estimating LDL-C in samples with extreme HDL-C concentrations due to absence of statistical correlation with LDL-C direct measurement.

► Friedewald Formula is the most usual approach in clinical routine to calculate LDL-C.
► Different limitations of FF have been reported.
► We evaluated the effect of extreme low or high HDL-C levels on LDL-C estimation.
► Estimation formulas should not be used to calculate LDL-C with extreme HDL-C levels.