Comparison of LDL - cholesterol estimated by direct method and by calculation

Abstract

Introduction: Total cholesterol (TC) and Low-density lipoprotein cholesterol (LDL-C) are well-established risk factors for the coronary heart disease (CHD). There are many homogenous assays currently available for the estimation of serum LDL-C. Most clinical laboratories determine LDL-C (mg/dL) by Friedewalds formula (FF), LDL-C = (TC) - (HDL-C) - (TAG/5). This formula shows the level of LDL-C is dependent on triglyceride (TAG) level. Aim and Objectives: The aim of this study was to find out the relative advantages of direct measurement of cholesterol over the conventional derivation of LDL-C by calculation. Material and Method: The study contained 80 participants above 18 years. LDL-C estimation was done by direct method manually on the spectrophotometer and also calculated using the Friedewalds Formula. An independent t-test was applied to find out the statistically significant difference. Results: It was observed that, the mean LDL-C levels by calculated method and the direct method in the control group (TAG?150 mg/dl) (114.83 and 116.88 mg/dl respectively, P=0.81), case group-1 (TAG=150-300 mg/dl) (113.11and 116.01 mg/dl respectively, P=0.82) and case group-2 (TAG=300-400 mg/dl) (112.75and 116.30 mg/dl respectively, P=0.73) show no significant difference, but in the case group-3 (TAG?400 mg/dl) (112.12 and 182.0 mg/dl respectively, P 0.001) shows significant difference. Conclusion: Our data suggest that; the estimated LDL-C can be substantially underestimated due to the high triglyceride levels of 400 mg/dl or more. These results in the misclassification of the risk, where the patients calculated LDL-C may be lower than their true LDL-C, resulting in the missed opportunities for the treatment.