Study on Setting up the Reference Method of Catalytic Concentration of Alanine 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 alanine aminotransferase(ALT).Methods To establish the reference method to measure catalytic concentration of ALT at 37℃ according to IFCC primary procedure.In order to verify the accuracy of the reference method,measured ERM○ R-AD 454 ALT by using the reference method.The relevant methodological parameters such as the precision,linearity and interference of the reference method were analyzed.At the same time,a calibrator was prepared and its value for ALT 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 ALT at 37℃.The result of measuring ERM○ R-AD 454 ALT was 186.4 U/L and the value of ERM○ R-AD 454 ALT was 186±4 U/L.Got 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 ALT was about 32 U/L and the biases of measurement were over 5%.The concentration of interfering substances were as below:free-bilirubin was 205.2 μmol/L and conjugated-bilirubin was 136.8 μmol/L.When ALT was about 123 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 and conjugated-bilirubin was 273.6 μmol/L.When hemoglobin was about 2 g/L,both concentrations of ALT varied more than 5%.When Triglyceride was below 10 mmol/L,it did not affect the result of measurement.The correlations of the routine method that was calibrated by the prepared calibrator and the reference method were well(r2=0.999 2).And the relative biases of both results were±10%.Conclusion The reference method of ALT(37 ℃)has been already established.Accuracy and comparability of ALT measurements can be improved by using a calibrator that was assigned by the reference method.