Importance Of Calibrations With Traceability And Commutability In A Clinical Biochemical Test

Background: Enzymology standardization method is an important factor to solve the results comparable between laboratories, The results of serum enzyme tests vary with conventional measurement systems. This may result because various reagent manufacturers have different reagent buffer types and concentrations, or different sample/reagent volume ratios. In addition, the precision of various colorimetric assays and the constant temperature performance in various reaction baths may differ. And each calibration of manufacturers has different traceability, different traceability chain, and it causes the product calibration traceability is quite different. Eventually lead to poor comparability between clinical results, and was a big barriers between different hospitals.To improve the comparability of serum enzyme tests, the International Federation of Clinical Chemistry(IFCC) studied and published multiple reference methods for enzyme tests, and standards for the preparation of reference materials. With the establishment of the enzymology test standardized procedures, there are more and more experts were committed to the standardization research. The goal was to achieve comparability of test results from patient samples among different laboratories or different test procedures. However, although standardization is needed, an indispensable characterization of reference materials, and their commutability, has not been done.Objective: This study that attempting to prepare good traceability and commutability of serum matrix for reference materials, and use this reference materials to calibration clinical routine methods, In order to improve the accuracy of the laboratory testing results and the precision of the results between laboratories, further improve the results consistency and comparability between different hospitals.Methods: Mixed serum samples of GGT, CK and LDH all negative for Hbs Ag, Anti-HCV, syphilis TP, and HIVAg/Ab, were collected. Evaluation of stability and verification of commutability and stored at-80?. Mixed serum assignment the value by reference laboratories for the calibration, which compared with the international well-known manufacturer calibration, after use the mixed serum in clinical laboratory the effect is equal to or better than other manufacturers calibration. Four enzyme reference laboratories performed value assignments to prepare reference material having traceability and commutability. The eleven participating laboratories used their own calibrations to calibrate their instruments and then measured the serum samples at low, middle, and high levels, they measured the reference materials too. After that the eleven participating laboratories used the reference materials to calibrate their instruments again. After calibration with reference materials with traceability and commutability, the serum samples at the low, middle, and high levels and the reference materials were again measured three times, and the results recorded. Test result biases of the reference material relative to the target value and the coefficient of variation(CV) of LDH, GGT, CK tests for serum samples at the low, middle, and high levels, from these eleven laboratories were calculated before and after calibration, using the reference material with traceability and commutability as calibration.Results: The reference materials has good stability and commutability, The GGT, CK, LDH activities of the mixed serum samples were measured in August 2014, November 2014, March 2015 and July 2015. The mean values of GGT were 133.88 U/L, the standard deviation(SD) was 0.63 U/L, and the CV was 0.47%; The mean values of CK were 151.60 U/L, the standard deviation(SD) was 0.33 U/L, and the CV was 0.22%; The mean values of LDH were 230.63 U/L, the standard deviation(SD) was 1.31 U/L, and the CV was 0.57%.The test results of CV of GGT, CK, LDH reference materials is very small among four reference laboratories. The mean values of GGT were 127.71 U/L, he standard deviation(SD) was 0.92 U/L, and the CV was 0.72%; The mean values of CK were 140.79 U/L, the standard deviation(SD) was 2.20 U/L, and the CV was 1.56%; The mean values of LDH were 226.95 U/L, the standard deviation(SD) was 1.52 U/L, and the CV was 0.67%. After the eleven participating laboratories used the reference materials with traceability and commutability as a calibrations to calibrate their instruments, and then measured the reference materials again. the mean values of GGT were 128.08 U/L, the Bias was 0.30 U/L, the mean values of CK were144.94 U/L, the Bias was 2.94U/L, The mean values of LDH were 227.49 U/L, the Bias was 0.23 U/L. After calibration using reference materials with traceability and commutability, the GGT test result bias decreased from 0.66% to 0.30%, the CK test result bias decreased from 4.18% to 2.94%, the LDH test result bias of the reference material relative to the target value decreased from-4.10% to 0.23%. The CVs of GGT values for the serum samples in the low, middle and high level decreased from 6.13%, 5.90% and 6.04% to3.30%, 1.18% and 1.83%, respectively; and The CVs of CK values for the serum samples in the low, middle and high level decreased from 3.76%, 4.19% and 4.96% to3.19%, 2.61% and 2.81%, respectively; The CVs of LDH values for the serum samples in the low, middle and high level decreased from 8.39%, 8.74% and 8.76% to1.14%, 1.21% and 2.73%, respectively.Conclusion: This study collected fresh mixed serum preparation of reference material, remove the impurities in the mixed serum after packing, verify the stability of the mixed serum and commutability. Four international RELA achievement eligible enzymology reference laboratories jointly assignment, multicenter joint assignment can eliminate deviation of test results caused by a enzymology reference laboratory.Use reference materials for each test system as calibration is feasible. This method is with recognized enzyme reference to one or more of the conventional method for determining the results the same as the reference method, the determination results of numerical and transmission between the reference method and conventional method to improve the conventional method and reference test results comparable between the most effective measures. For each lab devices standardization and consistency of the results.