Analytical performance and clinical application of glycated albumin detection by enzymatic method

Objective To verify the various performances of the enzymatic method that is used to detect the glycated albumin (GA) on automatic biochemistry analyzer and to apply it in clinic preliminary. Methods This verification study validated the limit of quantitation,linearity,imprecision,interferences (bilirubin,hemoglobin,chyle) of GA assay according to the CLSI EP17-P,EP6-A,EP15-A,EP7-P protocol. To assess the accuracy of GA assay,we used manufacturer′s secondary standard material and three level freeze-dry serum that values have been assigned using HPLC method.To determine the consistency of assay,50 fresh serum samples of outpatient in Mar 2012 were tested using this kit on four automatic biochemistry analyzer (BECKMAN AU5400,ROCHE MODULAR P,HITACHI7180,BECKMAN DXC600).According to the CLSI C28-A3 protocol,the reference ranges for GA% were validated in 452 apparently healthy individuals undertaking medical examination from Feb to Mar 2012.61 subjects with T2DM treated in the endocrinology department of PUMC Hospital from Oct. to Dec. 2012 were enrolled in the study.GA% and HbA1cwere determined respectively after they finished their 30-45 day oral hypoglycemic agent therapy.The correlation between GA% and HbA1cwere analyzed. Results The limit of quantitation was 0.028 g/dl; the linearity was 0.028-3.61g/dl (R2=0.9997); repeatability CV was 0.6%-1.5% and reproducibility CV was 1.3%-2.1%. The imprecision were lower than that declared by assay producer.When bilirubin≤659μmol/L, hemoglobin≤0.966μg/L and chyle turbidity≤1530 FTU,the deviation was -3.80%,-4.03%,-1.34% respectively.For the accuracy based tests,the bias% of enzymatic method were -1.2%-1.53%,when compared to HPLC.The regression equations of GA% were as follows: Y=1.0216X-0.0449 (R2=0.9991), Y=0.9963X+0.0423 (R2=0.9990),Y=0.9776X+0.075 (R2=0.9995), Y=1.0245X-0.0367 (R2=0.9906),respectively. The bias were 0.5%-3.3%,-2.4%-1.9%,-2.9%-0.7%,-1.9%-5.0% accordingly.The 95% confidence interval of the 452 apparently healthy subjects was 11.3%-15.6%.GA was significantly correlated with HbA1c (r=0.812,P<0.01).Linear regression analysis,produced a relationship of GA=2.345 HbA1c+1.549. Conclusions The enzymatic method that is used to detect the glycated albumin on automatic biochemistry analyzer has good performances of sensitivity,linearity,specificity,anti-interferences,and consistency among various analyzers.Which meet the clinical needs.Reference intervals were verified for use in our lab.(Chin J Lab Med,2013,36:343-347) Key words: Serum albumin; Clinical enzymetests; Reference value; Sensitivity and specificity