Work

Multi-Site Validation of a Newly FDA-Cleared Automated Methotrexate Immunoassay for Therapeutic Drug Monitoring

Year: 2025

Type: article

Abstract: BACKGROUND: Methotrexate (MTX), a synthetic antimetabolite and folic acid antagonist, has become a cornerstone in the management of malignant diseases. However, MTX toxicity can be severe and potentially life-threatening, especially with high-dose regimens used in oncology. Given its narrow therapeutic index, precise monitoring of MTX levels is critical to optimize efficacy while minimizing toxicity. METHODS: We validated the performance of the Roche ONLINE therapeutic drug monitoring (TDM) Methotrexate Assay on Cobas c502 and Cobas pro c503 platforms across 2 clinical sites, focusing on key analytical parameters such as linearity, accuracy, precision, dilution, carryover, and method comparison. RESULTS: The assay was linear across the analytical measurement interval (AMI) of 0.04-1.2 µmol/L. No significant carryover was observed (i.e., <5% bias). Automatic and manual dilutions demonstrated <10% bias, and the coefficients of variation (CVs) for precision and percentage bias for accuracy were <10%. A method comparison using 40 patient samples showed a strong correlation between the Roche and ARK MTX assays, with a Deming regression slope of 0.9634, an intercept of -0.0095, and Pearson correlation coefficient (r) = 0.9935, with a mean percentage difference (%Bias) of -12. Comparison with LC-MS/MS demonstrated high agreement for both assays. The ARK assay yielded a slope of 0.8873, an intercept of 0.0145, r = 0.9978, and %Bias of -6, while the Roche assay yielded a slope of 0.8541, an intercept of 0.0047, r = 0.9919, and %Bias of -18. CONCLUSIONS: The Roche ONLINE TDM MTX assay is a robust and clinically adequate method for methotrexate quantification and therapeutic drug monitoring.

Source: The Journal of Applied Laboratory Medicine

DOI: 10.1093/jalm/jfaf189

Authors: Shaimaa Maher, Vincent Buggs, Patrick Ravelo, Lu Song, Imir G Metushi

Institution: University of California, Los Angeles

Language: English

Topic: Clinical Laboratory Practices and Quality Control

Subfield: Physiology

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: hybrid

Estimated APC paid: $4,212