Infliximab Trough Levels Are Associated With Endoscopic Remission in Small Bowel Crohn's Disease.

Goals: To identify the association between infliximab trough levels (ITL) and treatment outcomes in small bowel Crohn's disease (SB-CD).

Background: Higher ITL are associated with favorable treatment outcomes in CD. However, the association between ITL and SB-CD treatment outcomes are rarely studied.

Study: This was a retrospective cross-sectional study. Patients with SB-CD who received maintenance infliximab therapy were recruited, and treatment efficacy was evaluated through double balloon endoscopy. Serum samples were collected to test ITL. The primary outcome was endoscopic remission (ER), which is defined as a Simple Endoscopic Score of Crohn's disease (SES-CD) of <3. The secondary outcome was mucosal healing (MH) (SES-CD: 0) and endoscopic response (SES-CD decreased by 50% from baseline). The factors associated with ER were also explored through logistic regression analysis.

Results: In total, 111 patients with SB-CD were enrolled. Forty-seven patients (42.3%) achieved ER. Median ITL was significantly higher in patients with ER than patients without ER (2.74 vs. 1.12 µg/mL, P<0.01). In a multivariate model, an elevated ITL was the only independent factor associated with an increased probability of ER [odds ratio (OR): 1.24, 95% CI: 1.08-1.43, P=0.003]. The cutoff level of ITL used to predict ER with a specificity of >80% was 3.45 µg/mL, and the area under the curve (AUC) was 0.790. Meanwhile, the AUC cutoff to predict MH and endoscopic responses was 0.767 and 0.759, respectively.

Conclusions: There was a significant association between higher ITL and favorable SB-CD treatment outcomes.