The Friedewald Formula Underestimates LDL Cholesterol at low Concentrations


Due to recent advances in the treatment of hypercholesterolemia, low density lipoprotein (LDL) cholesterol concentrations below 2.6 mmol/l have become attainable. In general, LDL cholesterol is determined indirectly according to Friedewald. We examined the performance of the Friedewald formula at low concentrations of LDL cholesterol in comparison with a β-quantification method. We analyzed 176 samples from individuals treated by LDL apheresis with a mean LDL cholesterol concentration of 3.07 mmol/l and found that the Friedewald formula underestimated LDL cholesterol with a bias of −18.5%, −14.5%, −7.3%, and −3.8% at mean LDL cholesterol levels of 1.58, 2.4, 3.49, and 4.67 mmol/l, respectively. Thus, the lower the LDL cholesterol concentration was, the greater the negative bias. We conclude that the Friedewald formula may not be reliable at low LDL cholesterol concentrations produced by LDL apheresis. This finding may also be of relevance to the monitoring of patients being treated with lipid lowering drugs.

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Clinical Chemistry and Laboratory Medicine ( CCLM) publishes articles on novel teaching and training methods applicable to laboratory medicine. CCLM welcomes contributions on the progress in fundamental and applied research and cutting-edge clinical laboratory medicine. It is one of the leading journals in the field, with an impact factor of over three. CCLM is the official journal of nine national clinical societies and associated with EFLM.