title: Therapeutic drug monitoring of infliximab: performance evaluation of three commercial ELISA kits.
abstract: BACKGROUND
  Therapeutic drug monitoring (TDM) of infliximab (IFX, Remicade®) can aid to optimize therapy efficacy. Many assays are available for this purpose. However, a reference standard is lacking. Therefore, we evaluated the analytical performance, agreement and clinically relevant differences of three commercially available IFX ELISA kits on an automated processing system.
  
  
  METHODS
  The kits of Theradiag (Lisa Tracker Infliximab), Progenika (Promonitor IFX) and apDia (Infliximab ELISA) were implemented on an automated processing system. Imprecision was determined by triplicate measurements of patient samples on five days. Agreement was evaluated by analysis of 30 patient samples and four spiked samples by the selected ELISA kits and the in-house IFX ELISA of Sanquin Diagnostics (Amsterdam, The Netherlands). Therapeutic consequences were evaluated by dividing patients into four treatment groups using cut-off levels of 1, 3 and 7 μg/mL and determining assay concordance.
  
  
  RESULTS
  Within-run and between-run imprecision were acceptable (≤12% and ≤17%, respectively) within the quantification range of the selected ELISA kits. The apDia assay had the best precision and agreement to target values. Statistically significant differences were found between all assays except between Sanquin Diagnostics and the Lisa Tracker assay. The Promonitor assay measured the lowest IFX concentrations, the apDia assay the highest. When patients were classified in four treatment categories, 70% concordance was achieved.
  
  
  CONCLUSIONS
  Although all assays are suitable for TDM, significant differences were observed in both imprecision and agreement. Therapeutic consequences were acceptable when patients were divided in treatment categories, but this could be improved by assay standardization.
authors.forename: Ellen M H
authors.initials: EM
authors.lastname: Schmitz
authors.forename: Daan
authors.initials: D
authors.lastname: van de Kerkhof
authors.forename: Dörte
authors.initials: D
authors.lastname: Hamann
authors.forename: Joost L J
authors.initials: JL
authors.lastname: van Dongen
authors.forename: Philip H M
authors.initials: PH
authors.lastname: Kuijper
authors.forename: Luc
authors.initials: L
authors.lastname: Brunsveld
authors.forename: Volkher
authors.initials: V
authors.lastname: Scharnhorst
authors.forename: Maarten A C
authors.initials: MA
authors.lastname: Broeren
mesh_terms: D016903:Drug Monitoring / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005765:Gastrointestinal Agents / Q000097:blood*; D006801:Humans; D000069285:Infliximab / Q000097:blood*; D009426:Netherlands; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic
chemical_list: D005765:Gastrointestinal Agents; D011933:Reagent Kits, Diagnostic; D000069285:Infliximab