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Descoeur J, Dupuy AM, Bargnoux AS, et al. 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. J Oncol Pharm Pract. 2021;28(1):55-63doi: 10.1177/1078155220983407.
Descoeur, J., Dupuy, A. M., Bargnoux, A. S., Cristol, J. P., & Mathieu, O. (2022). 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. Journal of oncology pharmacy practice : official publication of the International Society of Oncology Pharmacy Practitioners, 28(1), 55-63. https://doi.org/10.1177/1078155220983407
Descoeur, Juliette, et al. "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." Journal of oncology pharmacy practice : official publication of the International Society of Oncology Pharmacy Practitioners vol. 28,1 (2022): 55-63. doi: https://doi.org/10.1177/1078155220983407
Descoeur J, Dupuy AM, Bargnoux AS, Cristol JP, Mathieu O. 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. J Oncol Pharm Pract. 2022 Jan;28(1):55-63. doi: 10.1177/1078155220983407. Epub 2021 Jan 11. PMID: 33427019.
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J Oncol Pharm Pract. 2022 Jan;28(1):55-63. doi: 10.1177/1078155220983407. Epub 2021 Jan 11.

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.

Journal of oncology pharmacy practice : official publication of the International Society of Oncology Pharmacy Practitioners

Juliette Descoeur, Anne-Marie Dupuy, Anne-Sophie Bargnoux, Jean-Paul Cristol, Olivier Mathieu

Affiliations

  1. Department of Clinical Pharmacology, University Hospital of Montpellier, Montpellier, France.
  2. Department of Biochemistry, Centre Ressources Biologiques de Montpellier, University Hospital of Montpellier, Montpellier, France.
  3. PhyMedExp, University of Montpellier, Montpellier, France.
  4. Hydrosciences Montpellier (HSM), University of Montpellier, Montpellier, France.

PMID: 33427019 DOI: 10.1177/1078155220983407

Abstract

OBJECTIVES: 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.

METHODS: Following routine measurement with Abbott TDxFLx® assay (MTX-TDX), 62 samples were analysed on Architect®i1000 (MTX-ARCHI), Xpand® (ARK/XPND), Indiko® (ARK/INDI), and HPLC (MTX-HPLC) as the reference method. The influence of 7-hydroxymethotrexate was explored on ARK reagent to document the cause of the observed bias. ROC curves were built to study the impact of the method on the discharge thresholds for the patients at three levels.

RESULTS: Total imprecision was below 2.60% for the methotrexate-ARCHI and close to 10% for both ARK assays for plasma pools. The correlation coefficients were 0.93, 0.93, 0.89 and 0.95, the Bland-Altman difference plot revealed a bias of 0.075, 0.037, 0.049 and -0.002, and the number of results exceeding the TE criteria of 0.1 µM was 17 (27%), 13 (21%), 15 (24%) and 15 (24%) for MTX-TDX, ARK/INDI, ARK/XPND and MTX-ARCHI, respectively. Cross reactivity with 7-hydroxymethotrexate was between 1 and 9%. Overestimation of methotrexate concentration was between -4% and +32%. The most robust clinical level was found to be the highest level (0.2 µM) with ROC curves.

CONCLUSIONS: The authors found the best results for imprecision with chemiluminescent microparticle immunoassay method on methotrexate-ARCHI, with bias below to the RICOS recommendations and best correlation to the reference method. Impact on the threshold values for clinical decision need to be clearly exposed to clinicians.

Keywords: Methotrexate; Therapeutic Drug Monitoring; assays comparison; clinical thresholds

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