Background: Loss of clinical response and infusion reactions to infliximab are associated to Anti-IFX antibodies (ATI). ATI detection is a key step of patient management algorithm . However, current techniques require additional patient appointments for sample collection, processing and batching in centralised facilities. Test reporting usually takes several days or weeks impairing effective decision making. Here we validate the use of capillary blood in a real-life point-of-care (POC) setting where patients attend the infusion centre for Remicade® (RMC) or CT-P13 infusions.
Methods: PQ-EF2 is a prospective, observational study designed to evaluate the performance of a rapid POC test (Promonitor® Quick Anti-IFX, Progenika, Spain) to detect ATI in routine clinical practice in IBD and rheumatic patients treated with RMC or Inflectra® attending the infusion centre with the reference ELISA. The POC test is a qualitative immunochromatographic assay based on lateral flow technology to detect ATI (including biosimilar CT-P13) in either fingerprick or serum. Consecutive patients (initiating or under maintenance therapy) were recruited and tested with the rapid test in venous and capillary whole blood specimens immediately before the infusion. ATI test results were read visually with the POC test in 30 min, just before the patient started the infusion. Trough sera were also collected for subsequent analysis with the rapid test and benchmarked with Promonitor®-Anti-IFX ELISA. Follow-up time was 6 months. ELISA quantitative results were categorized as positive and negative to allow comparisons with the qualitative rapid test.
Results: Fifty four consecutive patients (21 IBD (13 Crohn's disease, 8 ulcerative colitis), and 33 with rheumatic diseases) were recruited (a total of 101 visits in the 6 months follow-up) accounting for a total of 101 sera, 101 fingerpricks and 35 venous whole blood samples. Overall, 4 (7.4%) patients developed ATI (1 CD, 1 UC, 2 ankylosing spondylitis). ATI were detected in 3 patients treated with RMC and 1 treated with Inflectra®. Overall agreements between fingerprick vs venous whole blood and fingerprick vs serum measured with the rapid POC test were 100% and 98%, respectively. Positive (PPA) and negative (NPA) agreements between the POC test and ELISA were 86% and 99%, respectively. PPA and NPA between the ELISA and the POC test in serum was 100% and 99%, respectively.
Conclusions: ATI can be reliably detected in either venous or capillary circulation. Results show an almost perfect agreement between specimens and with the reference ELISA technique. ATI measurement with the POC test allows the clinician to detect ATI in a quick and fully decentralized mode facilitating immediate POC decision making.
 Vande Casteele, (2015), Trough concentrations of infliximab guide dosing for patients with inflammatory bowel disease, Gastroenterology, 1320–9, 148