Comparison of Equations for the Calculation of LDL-Cholesterol in Familial Hypercholesterolemia: Data from Iranian Registry

Abstract

OBJECTIVE: Low-density lipoprotein cholesterol is the mainstay of diagnosis, treatment, and follow-up of patients with familial hypercholesterolemia, the most prevalent autosomal domi- nant disorder among humans. Since the reference measurement method (ultracentrifugation) is time-consuming and expensive, many formulas emerged to calculate low-density lipopro- tein cholesterol levels and are commonly used in laboratories. METHODS: To compare the performance of 3 low-density lipoprotein cholesterol calcula- tion equations with a direct method (enzymatic photometric assay), the lipid profiles of 1148 patients of the registry of familial hypercholesterolemia in Iran were analyzed retrospec- tively, 270 of which had a possible or definite familial hypercholesterolemia diagnosis according to Dutch criteria. While measured using the direct method, we calculated the low-density lipoprotein cholesterol levels using the Friedewald, Chen, and Anandaraja formulas. RESULTS: Our results showed that all 3 formulas are highly correlated with the direct method, and the Chen formula showed the highest intra-class correlation coefficient among all (0.954 among all patients with hypercholesterolemia and 0.947 among the familial hyper- cholesterolemia population). In addition, the Chen formula was the most sensitive, and the Friedewald formula was the most specific formula using a low-density lipoprotein cholesterol cut-off of 100 in familial hypercholesterolemia patients. CONCLUSION: Our findings encourage applying the Chen formula in addition to the Friedewald formula to make better clinical decisions for familial hypercholesterolemia patients.