Background Loss of clinical response and infusion reactions to infliximab (IFX) are associated to the development of antibodies to IFX (ATI). ATI detection is a key step of patient management. However, current techniques may 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.
Objectives To clinically validate the use of a new rapid test to detect ATI in capillary blood in a real-life point-of-care (POC) setting where patients attend the infusion center for the reference IFX (Remicade®, RMC) or CT-P13 (Inflectra®, IFT, or Remsima®) infusions.
Methods PQ-EF1 and PQ-EF2 are prospective, observational studies designed to evaluate and compare the performance of a rapid POC test (CE-marked Promonitor® Quick Anti-IFX, Progenika, Spain) to detect ATI in routine clinical practice in rheumatic and gastroenterology patients treated with the reference IFX or the biosimilar CT-P13 attending the infusion center with the ELISA technique as a reference. 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 or venous whole blood. Consecutive patients (initiating or under maintenance therapy) were recruited and tested in La Paz and Basurto University hospitals with the rapid test in capillary and venous 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 (Progenika, Spain). Follow-up time was 6 months. ELISA quantitative results were categorized as positive and negative to allow comparisons with the qualitative rapid test.
Results Ninety consecutive patients were recruited (a total of 137 visits in the 6 months follow-up) accounting for a total of 137 sera, 137 fingerpricks and 71 venous whole blood samples. Overall, 8 (8.9%) patients developed ATI (5 ankylosing spondylitis, 1 Crohn's disease, 1 ulcerative colitis and 1 juvenile idiopathic arthritis). ATI were detected in 5 patients treated with Remicade® and 3 treated with Inflectra®. Overall agreements between fingerprick vs venous whole blood and fingerprick vs serum measured with the rapid POC test were 100% and 99%, respectively. Positive (PPA) and negative (NPA) agreements between the POC test and ELISA were 91% 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 decentralised mode facilitating immediate POC decision making.
Disclosure of Interest A. Ametzazurra Employee of: Employee of Progenika Grifols, N. Rivera: None declared, A. Balsa: None declared, M. Arreba: None declared, E. Ruiz: None declared, C. Plasencia: None declared, J. Ortiz: None declared, D. Pascual-Salcedo: None declared, M. Muñoz: None declared, C. De Aysa: None declared, M. Allande: None declared, N. Torres Employee of: Employee of Progenika Grifols, A. Hernández Employee of: Employee of Progenika Grifols, X. Recalde Employee of: Employee of Progenika Grifols, A. Martínez Employee of: Employee of Progenika Grifols, D. Nagore Employee of: Employee of Progenika Grifols