Evaluation of serum gamma-glutamyltransferase assays by using the International Federation of Clinical Chemistry and Laboratory Medicine reference method

Objective To evaluate the measurement accuracy of serum gamma-glutamyltransferase (GGT) assays manufactured in China. Methods The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference method for GGT was set up and, after verification, was used to evaluate the performance of routine assay systems made in China. The evaluation was performed twice before and after a calibration by a common serum calibrator. Results For the reference measurement, the within run and total CVs were all less than 1%. The biases with the target values of IFCC External Quality Assessment Scheme for Reference Laboratories (RELA) were all within the limit of equivalence. Before a calibration with a common calibrator, the largest biases of results of GGT of the routine tasting systems compared with reference method at three medical decide levels were -47.53%, -34.11% and -30.07% respectively, and the averaged biases were 14.53% ,12.88% and 12.48%. After calibrating by fresh serum calibrator,the largest biases were reduced to - 17.63%, -5.88% and -4.08% ,the averaged biases were reduced to 7.50%, 2.70% and 1.87%. Conclusion The performance of GGT measurements can be effectively improved by using a common fresh serum calibrator that has a value assigned with the reference method. Key words: gamma-Glutamyltransferase;  Reference values;  Indicators and reagents;  Calibration