The Evaluation And Comparison Of Three Kinds Of Measuring Methods For Cystatin C

Objective:According to the EP documents of NCCLS,evaluate three kinds of measuring methods about Cystatin C.On the base of grasping the evaluating methods and being familiar with the process of operating,establish the evaluating methods in our lab.Methods:In terms of the EP documents of NCCLS,such as EP5-A(Evaluation of Precision Performance of Clinical Chemistry Devices),EP6-A(Evaluation of the Linearity of Quantitative Analytical Methods),EP7-P(Interference Testing in Clinical Chemistry),EP9-A(Method Comparison and Bias Estimation Using Patient Samples),to evaluate the precision,the detection limit,linearity,interference and accuracy of the three kinds of measuring methods.Results:①Reagent A:The within and between-day coefficients of variation(CV)varied from 0.98 to 1.46%and 1.35 to 2.25%,respectively.Reagent B:The within and between-day coefficients of variation(CV)varied from 3.54 to 6.28%and 5.93 to 9.22%,respectively. Reagent C:The within and between-day coefficients of variation(CV)varied from 0.65 to 1.55%and 0.77 to 1.51%,respectively.②The analytical sensitivity of reagent A and reagent B was 0.2mg/L.The analytical sensitivity of reagent C was 0.025mg/L.③No interference could be detected from Hb(up to 5g/L),TG(up to 19mmol/L),BIL(up to 200μmol/L),in reagent A and C.About reagent B,interference by TG and BIL was detected at 19mmol/L and 200μmol/L,respectively.④The assay was linear in the range 0.42-4.83mg/L by reagent A and B,less than the instruction.The assay was linear in the range 0.42-9.25mg/L by reagent C,and showed good correlation between theoretical and obtained values.⑤Comparing reagent A and reagent C,the calculated linear regression equation and the correlation coefficient were y = 0.9248x + 0.02385,and r= 0.9931,respectively.Comparing reagent B and reagent C,the calculated linear regression equation and the correlation coefficient were y = 0.8976x + 0.1382,and r= 0.9711,respectively.Conclusion:①Through the evaluation and comparison,there were many differences between our results and the instruction.So before we use a new reagent,we must to evaluate the index of system performance.②Reagent A showed good precision and accuracy in the linear range,so it can replace reagent C.③Established the evaluating methods about Cystatin C in our lab.