[Adaptation of methotrexate determination in plasma with Dimension Xpand]

The treatment with methotrexate at high doses is responsible of many side effects. It's necessary to evaluate serum methotrexate rate to monitor the administration of the methotrexate antagonist, the folinic acid. The aim of this study is to validate the determination of methotrexate in plasma using the automate Xpand Dimension (Dade Behring). Assay results were linearly related to the concentration for the wide range which was examinated (0.15 - 1.4 micromol/L). We report the precision, accuracy, linearity, sensitivity of this assay. The CV was less than 10%. We present the results of correlations with Aca (Dade Behring) and Cobas Mira (Roche). The reagent cartridge in the instrument and the calibration are stable during 28 days.