Traditional enzyme and fluorescence based immunoassays overestimate the concentration of methotrexate due to cross reactivity of the inactive metabolite 2,4-Diamino-N10methylpteroic acid (DAMPA). This cross reactivity emphasizes the importance of selective detection, which can be achieved with LC-MS/MS using the ACQUITY UPLC I-Class PLUS and Xevo TQD Mass Spectrometer in clinical research laboratories.
The antifolate methotrexate is a widely used drug for the treatment of various malignant tumors. Enzyme and fluorescence-based immunoassay tests are used to analyze methotrexate concentrations, but are known for their cross reactivity to the inactive metabolite 2,4-Diamino-N10methylpteroic acid (DAMPA).
Research on high-dose methotrexate (>500 mg/m2) for central nervous system (CNS) lymphoma is usually accompanied by the administration of glucarpidase or folinic acid rescue therapy to reduce methotrexate concentrations to below 1 mmol/L. Immunoassay techniques can overestimate methotrexate concentrations post-glucarpidase administration due to elevated levels of DAMPA, emphasizing the importance of using a selective detection method.
UPLC-MS/MS analysis with the ACQUITY UPLC I-Class PLUS and Xevo TQD provides the selectivity needed to achieve an accurate measurement of methotrexate.