title: Comparison of two methods of estimation of low density lipoprotein cholesterol, the direct versus friedewald estimation.
abstract: Current recommendations of the Adult Treatment Panel and Adolescents Treatment Panel of National Cholesterol Education Program make the low-density lipoprotein cholesterol (LDL-C) levels in serum the basis of classification and management of hypercholesterolemia. A number of direct homogenous assays based on surfactant/solubility principles have evolved in the recent past. This has made LDL-C estimation less cumbersome than the earlier used methods. Here we compared one of the direct homogenous assays with the widely used Friedewald's method of estimation of LDL-C to see the differences and correlation. We used direct homogenous assay kit to estimate serum LDL-C and high-density lipoprotein cholesterol (HDL-C). Serum Triglyceride (TG) and Total Cholesterol (TC) was estimated and using Friedewald's formula LDL-C was calculated. The LDL-C level obtained by both methods in 893 fasting serum samples were compared. The statistical methods used were paired t-test and Pearson's correlation.There was significant difference in the mean LDL-C levels obtained by the two methods at the TG levels <200 mg/dl (p<0.02) and TC levels >150 mg% (p<0.001). The correlation coefficient (r) between Friedewald's and direct assay estimation was 0.88. Friedewald's method classified 23.5 % of patients as high cardiac risk whereas there were 17.58% by direct assay.Both had good correlation even though the serum triglyceride and total cholesterol levels affect the difference in LDL-C estimated by both methods. Taking into account the cost and performance, Friedewald's method is as good or even better for classifying and managing patients.
authors.affiliation: Dept. of Biochemistry, Christian Medical College, 141 008 Ludhiana, Punjab India.
authors.forename: Suchanda
authors.initials: S
authors.lastname: Sahu
authors.forename: Rajinder
authors.initials: R
authors.lastname: Chawla
authors.forename: Bharti
authors.initials: B
authors.lastname: Uppal
keywords: Direct assay; Friedewald’s method; High-density lipoprotein cholesterol (HDL-C); Low-density lipoprotein cholesterol (LDL-C); Total cholesterol (TC); Triglyceride (TG)