Current status of therapeutic drug monitoring for methotrexate, imatinib, paclitaxel in China

Background: Accurate TDMs of plasma methotrexate, imatinib and paclitaxel assist in the development of optimal therapeutic regimes. This study aims to investigate the current status of methotrexate, imatinib and paclitaxel measurements in China and explore the suitable EQA materials for those drugs. Methods: 4 processed plasma samples including 2 levels of frozen pooled plasma samples and 2 levels of lyophilized pooled plasma samples were measured in different laboratories using different measurement systems. The inter-laboratory %CV and intra-measurement-system %CV of laboratories were calculated to assess the status of methotrexate, imatinib and paclitaxel measurements. The short-term stability and homogeneity of those processed samples were studied and compared. The relative differences (%) between the results of those two kinds of processed samples were also calculated to determine whether there were significant differences in their matrix effects for various measurement systems. Results: The mean inter-laboratory %CVs ranged from 12.8% to 15.3%, 14.7% to 19.6% and 56.8% to 81.6% for methotrexate, imatinib and paclitaxel, respectively. The intra-measurement %CV of homogeneous commercial measurement systems was better than other measurement systems. The lyophilized samples were more stable than frozen samples and there were no obvious differences in their matrix effects for most measurement systems. Conclusions: The agreement among the results of methotrexate, imatinib, and especially paclitaxel from different laboratories was not satisfactory. Currently, the lyophilized samples were the more suitable EQA material for methotrexate, imatinib and paclitaxel than frozen samples.

Automated summary

This study investigated the current status of methotrexate, imatinib, and paclitaxel measurements in China and compared different measurement systems. The results showed unsatisfactory agreement among different laboratories, and lyophilized samples were found to be more suitable as external quality assessment materials.