[Monitoring Serum Levels of Infliximab and Anti-Infliximab Antibodies in Pediatric Patients with Inflammatory Bowel Disease: Experience in a High Complexity Pediatric Hospital in Buenos Aires, Argentina].

Introduction: Infliximab is the most widely used drug in the treatment of patients with inflammatory bowel disease in pediatrics. Monitoring its levels is the best predictor of response to treatment and is an important resource to optimize its use, since loss of primary or secondary response is a factor to consider, especially in pediatrics where therapeutic options are limited. Aim: To evaluate in patients with inflammatory bowel disease the serum levels of infliximab and anti-drug antibodies during induction and maintenance, as well as their relationship with the different variables that may alter the clearance of the drug. Material and Methods: Prospective, descriptive, longitudinal, observational study, from October 2021 to February 2023. The population was divided into 2 groups: Group A was composed of patients in induction (determinations in weeks 12-15), and Group B was composed of patients in maintenance (determinations immediately before the next drug infusion). Blood levels between 3-7 ug/ml were considered adequate and anti-drug antibodies > 10 AU/ml were considered elevated. Results: Fifty-eight patients were included, 81.03% (n=47) with Crohn's disease and 18.9% (n=11) with ulcerative colitis. In Group A 20.6% needed treatment optimization and 19% showed loss of primary response, while in Group B , 64.4% showed loss of secondary response and the underlying mechanism of response could be determined, being immunogenic in more than 30% of patients. Conclusion: Knowing the levels of infliximab and anti-drug antibodies is a useful tool that in our experience has changed the course of patient management, allowing individualized follow-up and treatment.