ABSTRACT
Background: Meaningful underestimation of low-density lipoprotein (LDL) cholesterol is an important shortcoming of Friedewald’s formula (FF) at higher triglyceride (TG) levels. Recently a regression equation (RE) has been developed using lipid profiles in one setting and validated externally for the calculation of LDL cholesterol. This newly developed RE requires more studies in different settings. Objective: The aim of this study was to evaluate the performance of the regression equation against direct measurement. Materials and Methods: Lipid profiles of 600 subjects attending a tertiary healthcare center were included in this study. Specimens were collected and lipid profiles were measured by standard methods. Sixty two lipid profiles with TG above 400 mg/dL were excluded. Calculated LDL cholesterol values using FF and RE were compared with measured LDL cholesterol by Pearson’s correlation test, Passing & Bablok regression, accuracy within ±5% and ±12% of measured LDL cholesterol and two-tailed paired t test at various TG ranges. Results: The mean value of LDL cholesterol was 148.6 ± 37.2 mg/dL for direct measurement, 146.9 ± 42.4 mg/dL for FF and 148.6 ± 34.7 mg/dL for RE. The correlation coefficients of calculated LDL cholesterol values with measured LDL cholesterol were 0.949 (p<0.001) for FF and 0.959 (p<0.001) for RE. Passing & Bablok regression equation against measured LDL cholesterol was y = 0.897x + 16.2 for FF and y = 1.0842x – 13.1 for RE. Accuracy within ±5% of measured LDL cholesterol was 45% for FF, 57% for RE and within ±12% of measured LDL cholesterol was 84% for FF, 93% for RE. When calculated LDL cholesterol was compared with measured LDL cholesterol at different TG ranges, FF significantly underestimated LDL cholesterol at TG concentrations above 200 mg/dL whereas no significant difference was observed for RE. Conclusion: This study reveals that RE equation has similar performance to direct measurement for calculation of LDL cholesterol.
ABSTRACT
Background: Various formulas are available to estimate serum low-density lipoprotein (LDL) cholesterol. All of these are serum triglycerides (TG) dependent. But very recently de Cordova et al developed a simple formula (CF) to calculate LDL cholesterol without using serum TG and claimed it to be more accurate than Friedewald.s formula (FF). Objective: The objective of the present study was to evaluate the performance of the CF for the calculation of LDL cholesterol in a Bangladeshi population. Materials and Methods: Three hundred and sixty adult Bangladeshi subjects were purposively included in this study. Serum total cholesterol (TC), TG, high-density lipoprotein (HDL) cholesterol and LDL cholesterol were measured by direct automated methods. LDL cholesterol was also calculated by CF and FF. Results were expressed in conventional unit as mean ± SD and compared by two-tailed paired t test, bias against measured LDL cholesterol, Pearson's correlation coefficient (r), Passing & Bablok regression and accuracy within ±10% of the measured LDL cholesterol. Results: The mean values of directly measured LDL cholesterol, LDL cholesterol calculated by CF and FF were 117.7 ± 31.0, 111.8 ± 31.0 and 108.9 ± 39.7 mg/dL respectively. Bias of calculated LDL cholesterol against measured LDL cholesterol was -5.2% for CF and -9.6% for FF. The correlation coefficients of measured LDL cholesterol were 0.9796 (p<0.001) for CF and 0.9525 (p<0.001) for FF. Passing & Bablok regression yielded the equation y = 0.9938x - 6.2 for CF and y = 1.2774x - 40.9 for FF. Accuracy within ±10% of measured LDL cholesterol was 81% for CF and 49% for FF. Conclusion: This study revealed better performance of the de Cordova's formula than Friedewald's formula for approximate calculation of LDL cholesterol without using serum triglycerides.