Evaluation of Friedwald’ and Anandaraja’ formulae Against Direct Estimation of LDL in Fasting Samples Received in Aga Khan Multan Stat Lab
Keywords:
Low density lipoprotein cholesterol. Direct homogeneous assay. Friedewald formula. Anandaraja’s formula.Abstract
Objective: To compare the Friedewald and Anandaraja’s formulae with direct homogeneous assay for serum low density lipoprotein cholesterol (LDL-C) levels estimation.
Place and Duration of Study: A retrospective study was conducted from July 2012 to December 2012 at Multan Stat Laboratory of Aga Khan University Hospital
Method: The study assessed 1459 blood samples from out-patients of either gender sent to the Collection centers of Aga Khan university hospital, from southern Punjab for measurement of total cholesterol (TC), LDL-C, high-density lipoprotein cholesterol (HDL-C)’ VLDL and triglyceride (TG) levels. Total cholesterol, high-density lipoprotein cholesterol, TG and LDL-C were measured on Hitachi 902 chemistry analyzer (Roche). 68(4.66%) specimens with TG > 450mg/dl were excluded from further analysis .LDL-C levels were also calculated by Friedewald formula (FF) and Anandaraja’s formula in1391 samples. The mean± SD (mg/dl) LDL-C levels were calculated for three methods. The percentage difference (%ΔLDL) defined as calculated LDL-C minus D-LDL-C compared to the direct measurement was calculated using the following formula: %Δcalculated LDL-C = [(calculated LDL-C)-(DLDL- C)]/D-LDL-C*100.(26).Linear regression analyses was done using Microsoft Excel 2007 to assess the regression and correlations between three methods.
Results: Out of the 1391 samples for which analysis was done, 876 (62.97%) were received from the male patients and 415 (29.83%) were from females. Mean ± SD of age of the total study subjects was 46.08± 12.73years. Mean and standard deviation of D-LDL-C (110.88 ±37.37) is lower than mean and standard deviation of F-LDL-C (112.25±40.93 )and A-LDL-C (112.88± 39.77) . Mean percentage differences between Friedewald formula and Direct LDL-C values (∆F-LDL-C%) were positive (12.25±40.93) and mean percentage differences between Anandaraja’s formula and direct LDL-C values (∆A-LDL-C%) were also positive (12.88±39.77). A comparison of D-LDL-C (x) versus F-LDL-C (y) and D-LDL-C (x) versus A-LDL-C(y) values resulted in the following regression equations: y=-0.93516+1.053(X), r = 0.9623 and y =2.656717 +0.993985(X) , r = 0.9340, respectively .
Conclusion: On the basis of these findings, the D-LDL assay appears to be superior to the F-LDL-C and A-LDL-c assay .LDL-C should be measured by direct homogeneous assay in routine clinical laboratories.
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