Background: Recent developments concerning the quantification of anti-TNF-α therapies and auto-induced antibodies screening are crucial in inflammatory bowel disease (IBD) treatment. The formation of anti-infliximab antibodies (AIA) are associated with poor disease control. We aimed to assess if higher infliximab trough levels correlate with long term remission status. We wanted to test the hypothesis of different infliximab trough levels cut-offs in early and chronic therapy. Our objective also concerned the relevance of AIA and the preponderance of different factors (such as use of immunomodulators) in its presence.
Methods: Retrospective cohort study based on IBD patients treated with infliximab that were submitted to trough levels and anti-drug antibodies measurement. Remission was defined by the absence of symptoms and a C-reactive protein value ≤0.5 mg/dl. Statiscal work done with SPSS v. 20 (Chicago, IL USA), statiscal significance assumed with p value <0.05.
Results: 116 patients included, 56.8% women, mean age 39.4±13.3 (18–74) years; 85 patients with Crohn's disease (73.3%), patients with indeterminate colitis were excluded. All included patients were being treated with infliximab for at least 3 months after first administration, 59.5% patients were being treated also with immunomodulator. Mean 45.7±35.5 months of follow-up. For the entire group (116 patients) the isolated presence of AIA (in some cases temporarily) or the use of immunomodulators did not statiscal significantly affect remission, but the infliximab trough levels (p=0.009) affected, 1.72 μg/ml cut-off (0.632 area under ROC curve, p=0.016, 95% CI 0.530–0.735). When adjusted for the follow-up, in the period 3–12 months after induction the trough levels were an excellent remission marker (p=0.003) with a 1.87 μg/ml cut-off (0.855 area under ROC curve, p=0.006, 95% CI 0.680–1.0). However, for the long term period (>12 months after induction) higher trough levels did not correlate with comproved biochemical remission (0.576 are under ROC curve, p=0.215, 95% CI 0.460–0.692).
Conclusions: The infliximab trough levels showed good accuracy to optimize therapy in the period during or just after inducing remission but weren't very helpful in the period of maintenance. Our cut-offs for the trough levels were lower than the published before.