Determination of methotrexate in serum: the aca MTHO immunoassay and HPLC compared.

The determination of methotrexate on the aca clinical analyser (aca MTHO method) was evaluated and the method compared with a fluorescence polarisation immunoassay (FPIA) and a specific high-performance liquid chromatography (HPLC) procedure. The within series and the between days coefficients of variation of measurements in human pool serum spiked with methotrexate (0.07 mumol/l to 15 mumol/l) ranges from 11.7% to 2.5% and 14.0% to 5.8%, respectively. The calibration was found to be stable for 9 weeks. There was a good correlation between the results of the MTHO method when compared with FPIA and HPLC. At low methotrexate concentration, the results of HPLC were on average 11% and 14% lower than those obtained by the MTHO assay and FPIA respectively.