Introduction: Careful monitoring of drug concentration (therapeutic drug monitoring, TDM) is essential for a large number of drugs. The aim of this study was to evaluate analytical performance of Abbott AxSYM analyzer for therapeutic drug monitoring of theophylline, carbamazepine, pheno-barbital and valproic acid.
Materials and methods: For the purpose of analytical validation following parameters were determined for all analytes: inaccuracy (bias), within-run and between-run imprecision and measurement uncertainty. Additionally, concentration of valproic acid was compared with the previously used analytical system (TDx FLx Abbott analyzer) for 30 patients\u27 samples.
Results: Inaccuracy results (bias) were as follows: for theophylline from -3.66% to -5.84%; for carbamazepine -0.46% to 1.00%; for phenobarbital -1.83% to -8.08% and for valproic acid from -1.01% to -5.65%. The highest coefficient of variation (CV) for within run imprecision was observed for phenobarbital (7.07%) and the lowest for theophylline (2.71%). The highest CV for between run imprecision was observed for carbamazepine (4.73%) and the lowest for theophylline (2.94%). The highest measurement uncertainty was observed for phenobarbital assay (21.7%) and the lowest for carbamazepine (10.7%).
Passing-Bablock regression analysis of valproic acid comparison on two analyzers showed statistically significant, but clinically insignificant deviation in slope of the regression equation (b = 1.121; 95% CI = 1.028-1.197); however the Cusum linearity test proved that there was a linear relationship between two methods.
Conclusion: In conclusion, analytical validation fulfilled all previously established criteria and could be implemented in a routine laboratory work
