Assessment of various calculation methods for measurement of LDL-Cholesterol

Background: Coronary Artery Disease is the leading cause of death worldwide and LDL has been recommended as the primary lipid subset for prediction of risk of CAD NCEP guidelines. Many assays have been developed for measurement of LDL levels and have shown reasonable accuracy as compared to reference method but still not cost effective and cannot be affordable by majority of laboratories. Laboratories use the cost effective Friedewald’s formula for calculating the LDL instead of direct assay which give near to accurate value but has its own limitations. In recent days many newer formulae have come up with lesser limitations and here an attempt is made to evaluate these formulae and to correlate with direct measurement of LDL. Methodology:  It’s a cross sectional study. Sampling technique is Census method and involves sample size of 1020 cases. The entire lipid Parameters (LDL, HDL, TC, and TG) were estimated using Kits purchased by Roche /Cobas and then LDL also calculated using various formulae. Data was entered in Excel and analysed by Epi info software. Descriptive statistics like mean, standard deviation, standard error of mean were calculated. Student t test and Pearson’s correlation are used to find the correlation between measured LDL and calculated LDL at different intervals of TG, TC and HDL. Results: A total of 1020 samples were studied. The Cordova Formula correlated well in all the 1000 samples as a whole and in subjects with normal lipid profile and also at all lipid levels except for TG < 200mg/dl, TC < 100mg/dl. At TG < 200mg/dl Anandaraja’s formula shows better correlation and at TC < 100mg/dl none of the formulae performed well as all formulae negatively correlated with the direct measurement of LDL. Conclusion: Even though Cordova formula in our study has outperformed the other formulae, there are lots of factors which will affect the calculation. So it is highly recommended to switch to newer direct assays available in the market which ar