Infliximab trough levels among patients with inflammatory bowel disease in correlation with infliximab treatment escalation: a cross-sectional study from a Greek tertiary center.

Background: Infliximab monitoring correlates with improved outcomes in inflammatory bowel disease (IBD). We aimed to evaluate the association between serum infliximab trough levels (TLs) and therapeutic outcomes in Greek patients with Crohn's disease (CD) or ulcerative colitis (UC).

Methods: This cross-sectional study included consecutive adult patients with IBD receiving intravenous infliximab maintenance therapy at a Greek tertiary center. Therapeutic outcomes assessed were clinical remission (CR), steroid-free clinical remission (SFCR), biochemical remission (BR: C-reactive protein <5 mg/L), and combined (steroid-free and biochemical) remission (SFCBR).

Results: Seventy-seven patients participated (62.3% with CD, 16.8% on concomitant immunomodulators), with a mean infliximab infusion duration of 5.1±4.6 years. Forty-seven (61%) patients underwent treatment escalation. Infliximab mean TLs were 7.2±4.9 μg/mL, correlating only with treatment escalation (9.7 vs. 3.6 μg/mL, P<0.001). CR was achieved in 88.3% of patients, SFCR in 80.5%, BR in 62.3%, and SFCBR in 55.8%. In a subgroup analysis, for patients without treatment escalation, higher mean TLs were significantly associated with BR (4.2 vs. 0.8 μg/mL, P=0.020) and SFCBR (4.3 vs. 1.5 μg/mL, P=0.035). In receiver operating characteristic analysis, TLs predicted SFCBR (P=0.016) with good accuracy (area under the curve [AUC] 0.768, 95% confidence interval [CI] 0.584-0.952), with an optimal TL cutoff at 3.4 μg/mL. For patients with treatment escalation, TLs predicted SFCBR (P=0.018) with fair accuracy (AUC 0.653, 95%CI 0.527-0.755), with an optimal TL cutoff at 11 μg/mL.

Conclusions: Infliximab TLs correlate with treatment escalation. Higher infliximab TLs may predict combined remission among patients with treatment escalation.