Comparison of LDL Levels Obtained by Martin-Hopkins Formula and Friedewald’s Formula with Directly Measured LDL: A Cross-sectional Study

Abstract

Introduction: Low Density Lipoprotein (LDL) is one of the major modifiable risk factor of atherosclerotic diseases and so a potential therapeutic target. So, Low Density Lipoprotein Cholesterol (LDL-C) is of primary importance to assess cardiac risk. Many formulae are used to calculate LDL-C. Friedewald’s formula, despite its limitations, has been widely used due to its simplicity and convenience. The present research was aimed to compare the accuracy of Friedewald’s formula with the Martin-Hopkins formula, providing valuable insights for clinical practice. Aim: To compare LDL levels obtained by the Martin-Hopkins and Friedewald’s formula with LDL levels obtained by directly measuring LDL in the southern India. Materials and Methods: The present hospital-based cross-sectional study was conducted in the Department of Biochemistry, Hassan Institute of Medical Sciences (HIMS), Hassan, Karnataka, India, from March 2023 to June 2023. Total participants were assessed for their serum lipid profile using standard methods. LDL-C was calculated using the Friedewald and Martin formulae, and these calculated values were then correlated with the directly measured LDL-C. Based on Triglyceride (TG) levels, subjects were divided into five groups to ensure a comprehensive analysis (Group-1: TG <100 mg/dL, Group-2: TG=101-150 mg/dL, Group-3: TG=151-200 mg/dL, Group-4: TG=201-400 mg/dL, Group-5: TG >400 mg/ dL). Groups were compared using a correlation analysis using Pearson’s correlation and paired t-test. Results: The study findings are significant. At TG levels <100 mg/dL, the Martin formula demonstrated a superior correlation (r=0.964, p-value≤0.001). At TG 101-150 mg/dL, 151-200 mg/ dL, and 201-400 mg/dL, Friedewald’s formula showed a slightly better correlation. However, at TG >400 mg/dL, Friedewald’s formula had a higher mean difference. ROC curves further confirmed the superiority of Martin’s formula (AUC=0.948, p-value≤0.001), demonstrating better diagnostic performance than Friedewald’s formula (AUC=0.947, p-value≤0.001) at all TG levels. Conclusion: The Martin-Hopkins formula showed better diagnostic performance among the two equations than the Friedewald’s formula. The mean difference was lesser for Martin’s formula than Friedewald’s formula at all TG levels except at levels <100 mg/dL. Considering the mean difference, Martin’s formula provided better LDL-C values than Friedewald’s formula for estimating LDL-C in the present study’s demographic population.