P475 Rapid point-of-care anti-drug antibodies measurement correlates with standardised T tests and facilitate a proactive therapeutic drug monitoring approach in IBD patients on anti-TNF-α maintenance therapy

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Therapeutic drug monitoring (TDM) for anti-TNF α agents has emerged as a strategy to optimise treatment in IBD patients and involves measurements of drug levels and anti-drug antibodies (ADI). ADI detection has been associated with loss of response and infusion reactions. Current techniques to measure ADI require multiple samples and patient appointments; reporting takes several weeks delaying the decision-making process. We aimed to compare the performance of a point-of-care (POC) test with the ELISA assay in a group of IBD patients treated with infliximab (IFX). In this pilot, feasibility, double-centre study, a group of patients with Crohn’s disease (CD) or ulcerative colitis (UC) referred to the of IBD Unit of Azienda Ospedaliera di Padova and Gastroenterology Unit di Feltre ( BL) under Infliximab maintenance therapy were enrolled. Patients were evaluated immediately before the IFX-infusion and analysed for the presence of ADI with the POC-test (Promonitor Quick®, Progenika Biopharma-Grifols) and the well-established ELISA assay (Promonitor® anti-IFX and Promonitor IFX). Infliximab trough-levels (IFX-TL) were also analysed. According to the manufacturer, the lower limits of quantification were: POC = 23AU and ELISA-assay = 5AU. Clinical activity was defined according to Harvey–Bradshow Index (HBI) and partial Mayo score (pMS) in CD and UC patients, respectively; faecal calprotectin (FC) was also analysed. A total of 30 patients (mean age 46 ± 13,5; M/F 21/9; CD/UC 15/15) were tested. The POC-test found ADI in 11 (36.6%) patients, whereas the ELISA was positive for ADI in 12 (40%) patients; all patients positive for ADI showed low IFX TL according to published cut-off values (TL<3 μg/ml). No technical problems occurred during testing with both tested kits. The POC-test showed a good agreement with the comparative ELISA test. Overall, positive and negative per cent agreements between ELISA and POC test were 96.67%, 91.67% and 100% (Table 1), respectively. We also evaluated the relationship between clinical and biochemical activity with ADI presence according to POC test. No correlation was found between clinical activity (FC, HBI, and pMs) and presence/absence of ADI (Table 2) Table 1. Promonitor Quick ANTI-IFX(serum) and Promonitor ANTI-IFX ELISA (serum) comparison Table 2 POC can reliably detect the presence of ADI in high agreement with the ELISA tests. Indeed, ADI measurement by POC was also able to identify patients with low IFX-TL. POC testing allows immediate management of patients requiring Infliximab dose adjustment and should be implemented in daily clinical practice.

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