Abstract
Methotrexate (MTX) is an anticancer drug that interferes with nucleic acid metabolism and cellular proliferation. It is clinically important to monitor serum MTX concentration to avoid adverse effects. The basic performance of the newly developed homogeneous enzyme immunoassay “Nanopia® eTDM Methotrexate” (SEKISUI MEDICAL Co., Ltd.) for the quantitative determination of MTX was evaluated using an automated clinical chemistry analyzer. The within-assay coefficient of variation and day-to-day assay precision were 1.3–2.6% and 0.4–3.9%, respectively. The linearity was tested by serial sample dilution and was observed up to 1.20 μmol/L. There was no significant interference caused by the addition of the following interfering substances: 19.1 mg/dL free bilirubin, 21.9 mg/dL conjugated bilirubin, 504 mg/dL hemoglobin, and 1,620 FTU of chyle. There was excellent correlation between the Nanopia® eTDM Methotrexate assay and the fluorescence polarization immunoassay (Methotrexate-II/Dinapac TDx) with the linear regression analysis equation of y = 1.01x + 0.0003, with r = 0.995 using 62 patient samples. The Nanopia® eTDM Methotrexate assay showed sufficient basic performance for clinical use. Moreover, this assay may be beneficial in shortening the running time and in consolidating the laboratory test analyzer.
