title: Does LDL-C Estimation Using Anandaraja's Formula Give a Better Agreement with Direct LDL-C Estimation than the Friedewald's Formula?
abstract: Estimation of low density lipoprotein cholesterol (LDL-C) is crucial in management of coronary artery disease patients. Though a number of homogenous assays are available for estimation of LDL-C, use of calculated LDL-C by Friedewald's formula (FF) is common in Indian laboratories for logistic reasons. Recently Anandaraja and colleagues have derived a new formula for calculating LDL-C. This formula needs to be evaluated before it is extensively applied in diagnosis. We measured LDL-C by homogenous method (D-LDL-C) in 515 fasting samples. Friedewald's and Anandaraja's formulas were used for calculation of LDL-C (F-LDL-C and A-LDL-C, respectively). The mean LDL-C levels were 123.3 ± 53.2, 112.4 ± 50.2 and 109.2 ± 49.8 mg/dl for D-LDL-C, F-LDL-C and A-LDL-C, respectively. There was a statistically significant difference between the results (P > 0.001) obtained by calculation formulas compared to the measured LDL-C. There was underestimation of LDL-C by 10.8 and 14 mg/dl by Friedewald's and Anandaraja's formulas respectively. The Pearson's correlation between F-LDL-C and D-LDL-C was 0.931 and that between A-LDL-C and D-LDL-C was 0.930. Bland-Altman graphs showed a definite agreement between mean and differences of the calculation formulas and direct LDL-C with 95% of values lying with in ±2 SD limits. The mean percentage difference (calculated as {(Calculated LDL-C)-(D-LDL-C)}/D-LDL-C × 100) for F-LDL-C was maximum (-11.6%) at HDL-C ≥ 60 mg/dl and TG levels of 200-300 mg/dl (-10.4%) compared to D-LDL-C. A-LDL-C results gave highest mean percentage difference at total cholesterol concentrations <100 mg/dl (-37.3%) and HDL-C < 40 mg/dl (-17.1%), respectively. The results of our study showed that FF is better in agreement with D-LDL-C than Anandaraja's formula for estimation of LDL-C by calculation though both lead to its underestimation.
authors.affiliation: Department of Biochemistry, Gian Sagar Medical College & Hospital, Ramnagar, Distt. Patiala, Punjab 140601 India.
authors.forename: Shalini
authors.initials: S
authors.lastname: Gupta
authors.forename: Minni
authors.initials: M
authors.lastname: Verma
authors.forename: Kamaljit
authors.initials: K
authors.lastname: Singh
keywords: Anandaraja’s Formula; Friedewald’s formula; LDL-C
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