The Study Of The Establishment And Clinical Application Of Reference Method For The Measurement Of Catalytic Concentration Of Aspartate Aminotransferase

Objective:To establish a reference method at 37? and explore its best different determination modes on the analytic precision to measure the catalytic concentration of aspartate aminotransferase(AST).To analyze the methodological parameters and discuss its application in external quality assessment(EQA)Methods:According to IFCC primary reference procedure,to establish the AST reference method and improve its experimental conditions;9 different determination modes of A?I were designed according to different reading interval and mixing time after pipetting R2 reagent.The delay time is selected for 90 s and the continuous reading point is 180 s.The sample was measured and repeated twice a day for 20 consecutive days in each mode,to calculate the precision of the AST results in different measurement modes.The relevant methodological parameters such as the precision,accuracy and linearity of the reference method were analyzed by the NCCLS documents(EP5-A?EP15-A?EP6-A);Ten EQA samples from Shanxi Center for Clinical Laboratory in 2017 and five EQA samples from National Center for Clinical Laboratories(NCCL)in 2019 were measured by reference method and then the determined results were compared with the target values of EQA for the correlation analysis and bias evaluation according to the 1/2 total allowable error(Tea)of National Center for Clinical Laboratories to determine clinical acceptability of the reference methodResults:1.Shimadzu spectrophotometer,analytical balance,pH meter are all qualified by Shanxi Province Administration Of Quality Supervision Bureau.Optimization of reaction conditions:(1)When the temperature of the spectrophotometer temperature controller is 37.5?,the cuvette temperature is nearest to 37? and stable;(2)When the time of incubation is for 360 s,the temperature of the reaction solution is to 37?;(3)The determination bias of different pipettes meet the need of the required uncertainty2.The precision of 9 different measurement modes of A-I is 0.78%,0.7%,1.69%,1.21%,0.79%,1.55%,1.3%,0.79%,1.41%,respectively3.After optimizing the reaction conditions and determining the best measurement modes,the evaluation of the methodological parameters is implemented.The within-run and within-laboratory precision of the two batches(low-value and high-value)is<1%and<2%,respectively;The bias between the determinated results and the target values of Roche c.f.a.s calibration regent is within the given standards;The established reference method is linear in the range of 4-340 U/L4.There was a good correlation between the target values of EQA and the determined values by the established reference method for AST,and the correlation equation were Y2017=1.0106X+1.1078(R2=0.9988)and Y2019=1.0219X-0.7828(R2=0.9999)The relative bias of all batches were not exceeding 1/2 TEa of National Center for Clinical LaboratoriesConclusion:Different measurement modes have a significant influence on the AST result.The precision of the mode B in which the reading interval is 15 s and the mixing time is 45 s is the best;The AST reference method in our laboratory has been established and the methodological parameters(precision,accuracy as well as linear range)all meet the need of the requirements;The target values of EQA for AST can be accepted to some extent in China's EQA program.