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: Friedewald’s formula (FF) is used worldwide to calculate low-density lipoprotein cholesterol (LDL-chol). But it has several shortcomings: overestimation at lower triglyceride (TG) concentrations and underestimation at higher concentrations. In FF, TG to very low-density lipoprotein cholesterol (VLDL-chol) ratio (TG/VLDL-chol) is considered as constant, but practically it is not a fixed value. Recently, by analyzing lipid profiles in a large population, continuously adjustable values of TG/VLDL-chol were used to derive a novel method (NM) for the calculation of LDL-chol. Objective: The aim of this study was to evaluate the performance of the novel method compared with direct measurement and regression equation (RE) developed for Bangladeshi population. Materials and Methods: In this cross-sectional comparative study we used lipid profiles of 955 adult Bangladeshi subjects. Total cholesterol (TC), TG, HDL-chol and LDL-chol were measured by direct methods using automation. LDL-chol was also calculated by NM and RE. LDL-chol calculated by NM and RE were compared with measured LDL-chol by twotailed paired t test, Pearson’s correlation test, bias against measured LDL-chol by Bland-Altman test, accuracy within ±5% and ±12% of measured LDL-chol and by inter-rater agreements with measured LDL-chol at different cut-off values. Results: The mean values of LDL-chol were 110.7 ± 32.0 mg/dL for direct measurement, 111.9 ± 34.8 mg/dL for NM and 113.2 ± 31.7 mg/dL for RE. Mean values of calculated LDL-chol by both NM and RE differed from that of measured LDL-chol (p<0.01 for NM and p<0.0001 for RE). The correlation coefficients of calculated LDL-chol values with measured LDL-chol were 0.944 (p<0.0001) for NM and 0.945 (p<0.0001) for RE. Bland- Altman plots showed good agreement between calculated and measured LDL-chol. Accuracy within ±5% of measured LDL-chol was 49% for NM, 46% for RE and within ±12% of measured LDL-chol was 79% for both NM and RE. Inter-rater agreements (κ) between calculated and measured LDL-chol at LDL-chol <100 mg/dL, 100–130 mg/dL and >130 mg/dL were 0.816 vs 0.815, 0.637 vs 0.649 and 0.791 vs 0.791 for NM and RE respectively. Conclusion: This study reveals that NM and RE developed for Bangladeshi population have similar performance and can be used for the calculation of LDL-chol.
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.
ABSTRACT
Background: HbA1c can be measured by different methods. Enzymatic, boronate affinity chromatographic and cation-exchange high performance liquid chromatographic (HPLC) methods are considered as gold standard methods. To make the test cost-effective many laboratories use the immunological method installed in a chemistry analyzer. Objective: To compare the values of HbA1c measured by high performance liquid chromatographic method and immunological method in two laboratory settings. Materials and Methods: This observational and comparative study was conducted in Bangladesh Institute of Health Sciences (BIHS) and Enam Medical College, Savar, Dhaka. HbA1c levels measured by HPLC in BIHS were compared with that measured by immunological method in Enam Medical College, Savar, Dhaka. p values <0.05 were considered significant. Results: Statistically no difference was observed in mean HbA1c% between two methods in <7.0% HbA1c group and 7.1-10.0% HbA1c group. Significant statistical difference was found in mean HbA1c >10.0% group, but it was within acceptable limit. Conclusion: HbA1c can be measured by immunological method installed in an automated chemistry analyzer to make the test costeffective. But HPLC method is preferable.
ABSTRACT
Background: Abnormalities in lipid metabolism are associated with renal diseases. Association of serum lipid parameters with renal function is less studied in subjects with type 2 diabetes in Bangladeshi population. Objective: To assess the correlation of high density lipoprotein cholesterol with glomerular filtration rate (GFR) in type 2 diabetic subjects. Materials and Methods: One thousand three hundred thirty confirmed diabetic subjects advised for HbA1c, serum creatinine, serum total cholesterol, serum triglycerides, serum HDL cholesterol and LDL cholesterol were included in the study. Serum total cholesterol, HDL cholesterol, triglyceride, serum creatinine, HbA1c were measured by standard methods and serum LDL cholesterol was calculated by Friedewald’s formula. GFR was calculated by MDRD4 variables prediction equation. Total subjects were grouped according to sex; both males and females were subdivided into three subgroups depending on GFR values. Results of lipid parameters were compared by one-way ANOVA among different groups and correlation of lipid parameters with GFR were expressed by Pearson r. Results: HDL cholesterol was significantly different among different GFR groups (p<0.05) and positively correlated with GFR (r = 0.1386, p<0.001) in males. Total cholesterol and LDL cholesterol showed feeble positive correlation with GFR (r = 0.0789, p<0.05 for total cholesterol and r = 0.0768, p<0.05 for LDL cholesterol), but are not significantly different among GFR groups (p>0.05) in males. Total cholesterol, HDL cholesterol, LDL cholesterol, non-HDL cholesterol and LDLC/ HDL-C were significantly different among three different GFR groups (p<0.01) and only HDL cholesterol and LDL-C/HDL-C showed weak correlation with GFR (r = 0.0770, p<0.05 for HDL cholesterol and r = -0.0803, p<0.05 for LDL-C/HDL-C) in females. Conclusion: The study revealed that HDL cholesterol was significantly and positively correlated with glomerular filtration rate in both male and female diabetic subjects and assessment of lipid parameters might be a helpful tool to prevent or delay the progression of renal insufficiency.