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An Enzyme-Linked Immunosorbent Assay for Therapeutic Drug Monitoring of Infliximab

Ternant, David*; Mulleman, Denis* †; Degenne, Danielle* ‡; Willot, Stéphanie§; Guillaumin, Jean-Maurice*; Watier, Hervé* ‡; Goupille, Philippe* †; Paintaud, Gilles*

doi: 10.1097/01.ftd.0000189901.08684.4b
Original Articles
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An enzyme-linked immunosorbent assay (ELISA) measuring serum infliximab concentrations in treated patients was developed. Microtiter plates were sensitized with tumor necrosis factor α (TNF-α) and saturated with phosphate-buffered saline (PBS) containing 1% bovine serum albumin (BSA). Samples diluted 1:100 in PBS-1% BSA were added and bound infliximab was detected using peroxidase-conjugated goat anti-human immunoglobulin G specific for Fc fragment (HRP-anti hIgG). Reading was performed using an ELISA plate reader. The limit of detection, calculated by assaying 10 replicates of a drug-free serum sample or blank sample and defined as the lowest concentration distinguishable from zero at 2 standard deviations, was 0.014 μg/mL. Each quality control sample was tested on 7 occasions on 1 day and on 5 separate days. The intraday precision indices of the method were (percent coefficients of variation, CV%) 11.7%, 6.2%, and 6.9% for 0.04 μg/mL, 2 μg/mL, and 4.5 μg/mL, respectively. The corresponding bias measures (percent deviation) were −5.5%, −1.9%, and −7.9%, respectively. The between-days precision was 9.8%, 5.3%, and 5.3% for 0.04 μg/mL, 2 μg/mL, and 4.5 μg/mL, respectively. The corresponding bias were +0.3%, −0.3%, and −7.8%, respectively. Lower limit of quantitation and upper limit of quantitation were 0.04 μg/mL and 4.5 μg/mL, respectively. Trough serum concentrations of infliximab were measured in 6 adult patients with various diseases and in 5 pediatric patients with Crohn's disease. For the latter group, samples drawn 1 hour after the end of the infusion and repeated measurements also were available. Data were described using a 1-compartment population pharmacokinetic model. Terminal elimination half-life was 10.9 days. This method is rapid, accurate, and reproducible, and may be useful in therapeutic drug monitoring of infliximab.

*Université François-Rabelais, Immuno-Pharmaco-Genetics of Therapeutic Antibodies, Tours, France

Department of Rheumatology

Department of Immunology

§Department of Paediatrics, Tours University Hospital, Tours, France

Supported by Schering-Plough.

Reprints: Gilles Paintaud, Faculté de Médecine, Université François-Rabelais, 2 bis boulevard Tonnellé, F-37032 Tours cedex 1, France (e-mail: paintaud@med.univ-tours.fr).

Received for publication February 22, 2005; accepted September 21, 2005

© 2006 Lippincott Williams & Wilkins, Inc.