Comparison of Novel Equations for Estimating Low-density Lipoprotein Cholesterol in North Indian Population

Aim and background: Precise quantification of low-density lipoprotein cholesterol (LDL-C) is important for the management of cardiovascular diseases.Despite the availability of direct methods, most clinical laboratories use formula for LDL-C estimation.The Friedewald equation has been the widely used mathematical formula but has a stringent requirement for fasting sample and is not valid when triglycerides (TGs) >400 mg/dL.This study aimed to compare directly measured LDL-C with LDL-C estimated using novel equations-Friedewald, Martin-Hopkins, and Sampson formulae, and to propose a reliable formula for LDL-C estimation in the North Indian population.Methodology: This study is a retrospective analysis of lipid profiles from 500 patient samples received at a diagnostic laboratory.Low-density lipoprotein cholesterol was directly measured and compared with values calculated using the Friedewald, Martin-Hopkins, and Sampson equations.The compatibility between estimations was determined using correlation, Bland-Altman plot, and total error.Results: Our findings showed a positive, linear, and statistically significant (p < 0.001) correlation between directly measured LDL-C (d-LDL-C) and LDL-C calculated by the Friedewald, Martin-Hopkins, and Sampson's equation at three TG strata-<150 mg/dL, 150-199 mg/dL, and 200-499 mg/dL.At TG levels 500 mg/dL, the three formulae showed moderate positive linear correlation, which were statistically non-significant.Sampson formula had a relatively higher correlation at TG <150 mg/dL and 150-199 mg/dL, while Martin-Hopkins formula had overall better agreement with d-LDL-C results according to Bland-Altman test. Conclusion:The Sampson formula had better correlation at TG levels <150 mg/dL and 150-199 mg/dL.Also, this can be used at TG concentration up to 800 mg/dL, making it a suitable method.Clinical significance: This study provides comparative analysis of novel equations for calculation of LDL-C and recommends use of Sampson's equation as an alternative to Friedewald formulae for non-fasting patients and those with TG levels >400 mg/dL.