Guerriero Emilie, Simon Nicolas, Nelken Brigitte, Baldeyrou Brigitte, Djobo Bodalé, Vasseur Michèle, Allorge Delphine, Décaudin Bertrand, Odou Pascal
*Department of Pharmacy, Lille University Hospital; †Department of Antitumoral Pharmacology, Centre Oscar Lambret; ‡EA4481-GRIIOT, Department of Biopharmacy, Galenic and Hospital Pharmacy, Faculty of Pharmacy, Lille Nord-de-France University; §Department of Paediatric Haematology, Jeanne de Flandres Hospital, Lille University Hospital; and ¶Department of Toxicology, Biology and Pathology Center, Lille University Hospital, France.
Ther Drug Monit. 2014 Aug;36(4):499-504. doi: 10.1097/FTD.0000000000000053.
At this center, therapeutic drug monitoring of methotrexate (MTX) used to be performed by fluorescence polarization immunoassay (FPIA). We observed an increasing number of unusual high MTX concentrations at 48 and 72 hours during a couple of years. This study aimed to identify the causes of this variation.
A retrospective analysis was conducted on 272 patients hospitalized between January 2008 and October 2012. The whole MTX use system was analyzed using Ishikawa's method. The proportion of MTX concentrations ≤0.2 μmole/L at 48 (P48h) and 72 hours (P72h) was recorded and compared between both FPIA and EMITSiemens assays. A χ or a Fisher exact test was used (α = 0.05).
Because of an announced withdrawal of the FPIA reagent, the method was switched in 2009 to an immunoenzymatic technique (EMITSiemens). Both P48h and P72h dropped significantly after 2009 (P48h: 45% versus 5% and P72h: 91% versus 47%; P < 0.0001). The replacement of the EMITSiemens reagent by the EMITARK Diagnostics reagent in 2012 led to an increase in both P48h and P72h. No significant difference was found in the proportions of MTX ≤0.2 μmole/L concentrations between FPIA and EMITARK Diagnostics at 48 (45% and 40%; P = 0.556) and 72 hours (91% and 100%; P = 0.231). Both internal and external quality control assessments gave regular satisfactory results during the study period. Furthermore, the interassay comparisons that were performed with internal quality controls and spiked serum samples showed similar results at the time of both shifts. The other changes observed in the MTX circuit were not associated with MTX concentration variations.
The overestimation of the plasma concentration of MTX was concluded to be because of the assay reagent. A further study is consequently necessary to assess the impact of this analytical pitfall on the patients' survival.
在本中心，甲氨蝶呤（MTX）的治疗药物监测过去采用荧光偏振免疫分析法（FPIA）。在几年间，我们观察到48小时和72小时时MTX浓度异常升高的情况越来越多。本研究旨在找出这种变化的原因。
对2008年1月至2012年10月期间住院的272例患者进行回顾性分析。使用石川法对整个MTX使用系统进行分析。记录并比较FPIA和西门子酶放大免疫分析技术（EMIT西门子）在48小时（P48h）和72小时（P72h）时MTX浓度≤0.2微摩尔/升的比例。采用χ²检验或Fisher精确检验（α = 0.05）。
由于宣布停用FPIA试剂，2009年该方法改用免疫酶技术（EMIT西门子）。2009年后，P48h和P72h均显著下降（P48h：45%对5%，P72h：91%对47%；P < 0.0001）。2012年用EMIT ARK诊断试剂取代EMIT西门子试剂后，P48h和P72h均升高。在48小时（45%和40%；P = 0.556）和72小时（91%和100%；P = 0.231）时，FPIA和EMIT ARK诊断试剂检测MTX浓度≤0.2微摩尔/升的比例无显著差异。在研究期间，内部和外部质量控制评估结果均定期令人满意。此外，在两次方法转换时，用内部质量控制品和加标血清样本进行的批间比较显示结果相似。在MTX流程中观察到的其他变化与MTX浓度变化无关。
得出MTX血浆浓度被高估是由于检测试剂的结论。因此，有必要进一步研究评估这一分析缺陷对患者生存的影响。
