Objective To investigate the stabilization of betaine on the enzyme activity of ALT in human serum at different temperatures, and to evaluate the matrix effects of human serum with betaine among different analytical systems. Methods The enzyme activity of ALT in human serums with l mol/L betaine stored at 37 ℃, 25 ℃, 4 ℃ and - 20 ℃ respectively were measured. The matrix effect experiment was carried out according to the procedures specified in Clinical and Laboratory Standards Institute (CLSI)document EP14-A. Four analytical systems were the candidates for evaluation, and Roche Diagnostics (Roche)-Hitachi analytical system served as the reference system. The enzyme activity of ALT of 40 patient specimens and 3-level specimens ( high, medium and low) with 1 mol/L betaine were measured using the evaluated methods and the reference method respectively. The linear regression analysis was performed to compare the mean y value of 3-level specimens with the statistically defined limits ( the two-tailed 95% prediction interval) derived from 40 patient specimen data. Results The enzyme activity of ALT could be stabilized with betaine in serum, which remained to be 99% for 48 h at 37 ℃, 98% for4 d at 25 ℃, 97%for 4 weeks at 4 ℃, and 99% for 4 months at - 20 ℃. The enzyme activity of control serum decreased to 42%, 86%, 71%, 79% respectively. The mean y values of three specimens with the betaine were within the 95% prediction interval of the estimated mean y values, which suggested no obvious matrix effects in serum. Conclusion Betaine can be used in the development of enzyme ALT calibrator as its stabilizer.

Point-of-care testing (POCT) is one of the fastest growing disciplines of clinical laboratory medicine. It serves as a convenient tool for rapid clinical diagnosis. However, the increasing demand for POCT testing and the continuous expansion of the testing field has brought many new challenges to its quality management. This paper would introduce the problems existing in the clinical application of POCT, discuss the corresponding quality improvement suggestions and explore new thinkings for standardizing POCT management.