LOW-DENSITY LIPOPROTEIN CHOLESTEROL ESTIMATION BY FRIEDEWALDS FORMULA AND BY DIRECT MEASUREMENT - A COMPARISON

Introduction: Low-density lipoprotein cholesterol (LDL-C) levels in serum is the basis of diagnosis, classification and management of hypercholesterolemia as per the current recommendations of the Adult Treatment Panel III of National Cholesterol Education Program. Friedewalds formula is used in most laboratories to measure LDL-C levels indirectly. But, Friedewalds formula is not reliable always. Now-a-days, various homogenous assay kits for direct estimation of LDL-C based on precipitation and solubilisation using specific detergents have been evolved. This makes estimation of LDL-C levels easier but costlier. So we conducted a study to compare the results obtained by estimating LDL-C level by direct assay kit and also indirectly by using Friedewalds formula in order to assess the cost effectiveness of both the methods. Aim: To compare LDL-C levels obtained by direct homogenous assay (D-LDL-C) to that obtained by Friedewalds formula (F-LDL-C) in fasting serum samples. Materials And Methods: Serum separated from 404 blood samples was analysed for Total cholesterol (TC), Triglycerides (TG), High- density lipoprotein (HDL) and LDL using specific assay kits. Simultaneously, LDL-C was also estimated in the same samples indirectly by using Friedewalds formula. Results: Statistical analysis by Pearson correlation showed high correlation between D-LDL-C and indirect F-LDL-C. But in all ranges of TG, F-LDL-C showed underestimation of LDL-C when compared to D-LDL-C. Conclusion:Use of Friedewald formula for estimation of LDL-C is not suitable in all cases. In samples showing hypertriglyceridemia, direct homogenous assay was found to be better for CHD risk assessment and management.