Agreement in assessment of infliximab and adalimumab levels in rheumatoid arthritis: interlaboratory and interassay comparison.

Objectives: Infliximab (IFX) and adalimumab (ADL) drug levels and anti-drug antibodies (ADA) are assessed using a variety of techniques, therefore, results cannot accurately be compared for clinical purposes. The aim of this study was to test two infliximab (IFX) and adalimumab (ADL) ELISA versions, for drug levels and ADA, to see whether they yield similar results.

Methods: ELISA versions [Promonitor® IFX R1 and R2 (V.