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P309 High infliximab trough levels are associated with better control of inflammation in inflammatory bowel disease

D. Drobne*1, T. Kurent1, P. Rajar2, M. Slak3, M. Kozelj1, G. Novak1, N. Smrekar1, S. Plut1, A. Smid1, J. Osredkar4, B. Stabuc1, I. Ferkolj1

1University Medical Centre Ljubljana, Department of Gastroenterology and Hepatology, Ljubljana, Slovenia, 2University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia, 3Faculty of Pharmacy, Ljubljana, Slovenia, 4University Medical Centre Ljubljana, Clinical Institute of clinical chemistry and biochemistry, Ljubljana, Slovenia

Background

The target infliximab trough level to maximally control inflammation in inflammatory bowel disease (IBD) on infliximab maintenance treatment is unknown. Because data are conflicting, we aimed to study correlation of infliximab trough levels with faecal calprotectin and CRP, and to identify the target infliximab trough level needed for maximal control of inflammation.

Methods

Out of 286 prospectively followed infliximab-maintenance-treated patients with IBD in a tertiary referral university hospital, we identified 83 patients (42 CD, 35 UC, and 6 IBDU) who had infliximab trough levels (ELISA) (102 samples in 83 patients), faecal calprotectin (ELISA and POCT) (102 samples in 79 patients), and CRP (121 samples in 83 patients) measured within 60 days. We ranked infliximab trough levels in 3 numerically equal groups: low trough level (median 0.3 µg/ml [min 0.3 and max 2.0]), intermediate trough level (median 4.3 µg/ml [min 2.1 and max 6.0]), and high trough level (median 10.2 µg/ml [min 6.4 and max 12.0]). In each group we calculated median faecal calprotectin and CRP levels and proportion of patients with faecal calprotectin below 100 mg/kg and with normal CRP (≤ 5 mg/L). To test for differences across studied groups we used the Mann–Whitney U-test and Chi-squared test.

Results

Median faecal calprotectin levels and CRP were lower in patients with high infliximab trough levels (faecal calprotectin median 73 mg/kg [IQR 30–319]; CRP median 3 mg/L [IQR 3–6]) compared with patients with intermediate (faecal calprotectin median 140 mg/kg [IQR 56–461]; CRP median 3 mg/L [IQR 3–11]) and low infliximab trough levels (faecal calprotectin median 232 mg/kg [IQR 101–747]; CRP median 9 mg/L [IQR 3–26]) (faecal calprotectin p = 0.046; CRP p = 0.02). Similar was observed for proportion of patients with faecal calprotectin below 100 mg/kg and normal CRP.

Table 1. Proportion of patients with faecal calprotectin ≤ 100 mg/kg and CRP ≤ 5 mg/L across different infliximab trough concentrations


Conclusion

Our data indicate that infliximab trough levels > 6.4 µg/ml are associated with better control of inflammation (lower faecal calprotectin and CRP) in IBD on infliximab maintenance treatment compared with patients with lower infliximab trough levels.