Study on setting up the reference method of catalytic concentration of aspartate aminotransferase(37℃) and its application

Objective To investigate the efficacy of using a calibrator with values assigned with the reference method for improving the accuracy and comparability of serum aspartate aminotransferase(AST).Methods To establish the reference method to measure catalytic concentration of AST at 37℃ according to IFCC primary procedure.The relevant methodological parameters such as the precision,linearity and interference of the reference method were analyzed.To measure c.f.a.s by using the reference method and the reference ranges were known in the healthy peoples.At the same time,A calibrator was prepared and its value for AST was assigned with the reference method.results of 40 samples were compared between the routine method that was calibrated by the prepared calibrator and the reference method by EP9-A of NCCLS.Results The reference method was established elementarily to measure catalytic concentration of AST at 37℃,and to get the relevant methodological parameters:the total coefficients of variation(CV) were 0.89-1.12%;the linear ranges were 1.3-300 U/L.When AST was about 48 U/L and the biases of measurement were over 5%,the concentration of interfering substances were as below:free-bilirubin was 256.5 μmol/L,conjugated-bilirubin was 205.2 μmol/L;When AST was about 165 U/L and the biases of measurement were over 5%,the concentration of interfering substances were as below:free-bilirubin was 307.8 μmol/L,conjugated-bilirubin was 342 μmol/L.When hemoglobin was about 1 g/L;both concentrations of AST varied more than 5%.When Triglyceride was below 10 mmol/L,it did not affect the result of measurement.The result of measuring c.f.a.s was 128.5 U/L and the target value was 128 U/L.Reference range:male:10-40 U/L;female:7-40 U/.There were various differences between males and females in the groups of healthy subjects(P0.05).The correlations of the routine method that was calibrated by the prepared calibrator and the reference method were well(r2=0.9992).And the relative biases of both results were±10%.Conclusion The reference method of AST(37℃)has been already established in our lab.Accuracy and comparability of AST measurements can be improved by using a calibrator that was assigned by the reference method.