P-085 YI Infliximab Dosing Changes Based on Trough Levels in a Cohort of IBD Patients in Clinical Remission

Abstract

Infliximab is an effective treatment for both Crohn’s disease and Ulcerative Colitis. While infliximab levels are available clinically, it is not current practice to routinely monitor serum infliximab levels. It is not known if optimizing the dose of infliximab for patients in clinical remission has any benefits. We set out to describe trough levels of patients in clinical remission as well as changes in infliximab dosing after level checked. We developed a retrospective cohort of patients from a tertiary care IBD center in Boston, MA. We identified patients who had an infliximab level processed by Prometheus laboratories. Charts were reviewed regarding the details of the patient’s disease and management at the time of infliximab level. Patients were excluded if not currently on infliximab, infliximab was not a trough level (<5 days prior to infliximab infusion), or patient not in clinical remission at the time of the level. Data was analyzed with JMP Pro. We identified 49 patients who had at least one infliximab level checked while in clinical remission. The median age of the cohort was 35 (IQR: 30–45). The majority (63%) of patients were male. Most patients had Crohn’s disease (76%). Only 16 (33%) were on a concurrent immunomodulator. The median time on infliximab prior to first dose was 53 weeks (IQR: 30,177). Among the 49 patients, a total of 82 trough levels were checked in clinical remission. The median infliximab trough level for these patients was 5.6 µg/mL (IQR: 2.9–10.1), with 23 (28%) less than 3 µg/mL and 39 (48%) less than 5 µg/mL. Antibodies to infliximab were detected in 9 (11%) of infliximab trough levels. Thirty-one patients were in clinical remission for their first trough level, with a median value of 3.8 µg/mL (IQR: 0–7.1); notably 9 patients (29%) had undetectable trough levels. Of the 82 infliximab trough levels drawn in clinical remission, 25 (31%) levels resulted in a change of infliximab, with eighteen (67%) increases in infliximab therapy, 2 (7%) decreases in therapy, and 6 (22%) stopping. One patient was lost to follow-up (1%) prior to a change being enacted. Checking infliximab trough levels while in clinical remission resulted in a change in infliximab therapy in our cohort in approximately one-third of the time. While the optimal trough level of infliximab is not known, a number of patients in clinical remission will have low trough levels or antibodies to infliximab. Further studies are needed regarding the clinical benefit of dose optimization of infliximab in patients in clinical remission.