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P454. In IBD outpatients knowledge of fecal calprotectin and infliximab trough levels significantly enhances infliximab dose escalation decision making

V.W. Huang, C. Prosser, C. Shalapay, D.K. Fedorak, N. Dhami, H. Wang, K.I. Kroeker, R.N. Fedorak, University of Alberta, Medicine, Edmonton, Canada

Background

Infliximab is an effective, but costly, therapy for inflammatory bowel disease (IBD). It is dosed by weight (5 mg/kg) and administered every 8 weeks in the maintenance phase. Loss of response to infliximab will occur in over 50% of patients within 3 ys, resulting in infliximab dose intensification. Most often the decision for dose intensification is made on clinical assessment. Nevertheless, one third of patients with recurrent symptoms do not have actual disease recurrence. Furthermore, the presence of circulating infliximab is challenged by the inevitable development of antibodies to infliximab and the highly individual infliximab clearance rates.

The aim of this study was to determine if objective measures of inflammation using fecal calprotectin (FCP) and of the amount of infliximab using infliximab trough levels (ITL) would lead to different decisions than those made when only clinical assessment was available.

Methods

IBD patients receiving infliximab at the IBD infusion center were consented to provide stool and blood samples prior to their infusion. Stool FCP and blood ITL levels were determined by ELISA. At the time of the infusion an IBD clinician who did not have access to the FCP or ITL results provided a clinical assessment and recorded the actual clinical decision (ACD): no change vs. action (investigate, dose change, switch drugs). The ACD was then compared to: (1) an algorithmic decision where FCP >250 µg/g; ITL <2.0 or >7.0 µg/mL led to an action and, (2) a consensus decision by three expert IBD clinicians that incorporated FCP or ITL. Three-way concordance between the decisions was then determined.

Results

A total of 39 patients (27 CD, 12 UC) were assessed. Mean age 42.1±16.3 yrs; mean ITL 10.3±8.0 µg/mL; mean FCP 306.8±352.2 µg/g. Algorithmic FCP vs ACD decisions were discordant in 16/39 (41.0%) of the cases, and the algorithmic ITL vs ACD were discordant in (25/39) 64.1% of the cases. The Expert FCP vs ACD decisions were discordant in 18/39 (46.2%) of the cases, and the Expert ITL vs ACD decisions were discordant in 26/39 (66.7%) of the cases. Comparing the algorithmic decisions to the Expert IBD decisions revealed discordant decisions for FCP and ITL in 15/39 (38.5%) and 12/39 (30.8%) of the cases.

Conclusion

The addition of an infliximab trough level or a fecal calprotectin level, incorporated via a fixed algorithm or an expert IBD clinician often led to a different management decision compared to clinical assessment alone. Similar discordance rates were seen between the fixed algorithm and the expert IBD clinician. Given these differences in management decisions, the incorporation of fecal calprotectin and infliximab trough levels into daily care requires careful assessment of their effect on outcomes.