Comparison of four immunoassays to an HPLC method for the therapeutic drug monitoring of methotrexate: Influence of the hydroxylated metabolite levels and impact on clinical threshold.

This study focuses on comparison of four immunoassays to an hplc method for the therapeutic drug monitoring of methotrexate: influence of the hydroxylated metabolite levels and impact on clinical threshold.. The research employs high-performance liquid chromatography (HPLC) techniques to address analytical challenges in the clinical field. Methotrexate requires therapeutic drug monitoring in oncology because of narrow therapeutic index, especially the metabolite 7-hydroxymethotrexate exhibits nephrotoxicity. The goal of this study was to evaluate different assays and their impact on clinical decisions.... Research Background and Significance Methotrexate (MTX) is a cornerstone chemotherapeutic and immunosuppressive agent widely used in oncology and autoimmune diseases. Its narrow therapeutic index necessitates precise therapeutic drug monitoring (TDM) to optimize efficacy while minimizing toxic side effects. One significant challenge in MTX monitoring is the presence of its major metabolite, 7-hydroxymethotrexate (7-OH-MTX), which has been implicated in nephrotoxicity and can interfere with assay accuracy. Immunoassays, commonly used in clinical laboratories due to their ease and rapid turnaround, often suffer from cross-reactivity with this metabolite, potentially leading to inaccurate MTX measurements and suboptimal clinical decisions. This study by Descoeur et al. addresses this critical analytical gap by comparing four immunoassays to a validated high-performance liquid chromatography (HPLC) method, which is considered the gold standard for specificity and accuracy. The research aims to elucidate how hydroxylated metabolite levels influence assay results and the subsequent impact on clinical threshold determinations, thereby informing best practices in TDM for oncol