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* = Presenting author

P562 Real-life infliximab trough levels among inflammatory bowel disease patients on maintenance therapy: should we redefine therapeutic range based on inflammatory load?

Lobaton T.*1, Cañete F.1, Teniente A.2, Cabre E.1,3, Mañosa M.1, Martínez E.2, Domènech E.1,3

1University Hospital Germans Trias i Pujol, Gastroenterology, Badalona (Barcelona), Spain 2University Hospital Germans Trias i Pujol, Immunology, Badalona (Barcelona), Spain 3CIBER, Badalona (Barcelona), Spain

Background

Infliximab (IFX) trough levels (ITLs) have emerged as a promising tool for the management of inflammatory bowel disease (IBD) patients. However, optimal therapeutic range in clinical practice is still under debate and might vary depending on factors such as the inflammatory burden.

Methods

Observational study where IBD patients on maintenance IFX therapy were prospectively included from June 2015 to June 2016. Clinical and biological data including C-reactive protein (CRP) levels from the same infusion day were collected. ITLs were measured just before the infusion and where considered as infratherapeutic if they were <3 ug/mL. The aims were to describe real-life ITLs and to identify factors associated with infratherapeutic ITLs.

Results

A total of 235 infusions were analyzed among 77 patients (76% Crohn's disease). Median (IQR) disease and IFX duration was 10 years (5–18) and 23 months (7–61), respectively; 44% of patients had previous abdominal surgery; 88% received concomitant immunosuppressant therapy; and 35% presented also perianal disease. Median (IQR) ITLs and CRP levels were 0 ug/mL (0–1) and 3.1 mg/mL (1.5–6.1), respectively. Despite 61% of the patients were in clinical and biological remission, a total of 66% had infratherapeutic ITLs. Of note, loss of response occurred only in 28% of the cases. In the univariate analysis, being on a standard or reduced dose the presence of clinical and/or biological activity, and active smoking were associated with infratherapeutic ITLs. In the multivariate analysis, the presence of clinical and/or biological activity and active smoking remained as independent risk factors (Table 1). When analyzing only patients in clinical and biological remission and excluding those with an escalated dose, the proportion of patients with infratherapeutic ITLs was still high (56%) and smoking habit remained as a risk factor for these infratherapeutic ITLs.

Conclusion

In our cohort, more than half of the IBD patients on maintenance IFX therapy present infratherapeutic ITLs as conventionally defined, even among those in clinical and biological remission. Clinical and/or biological activity and active smoking were independent risk factors for ITLs <3. This highlights the strong impact of the inflammatory burden on ITLS and the need of re-defining the therapeutic range of ITLs, probably towards a more personalized method based on patient's characteristics such as inflammatory load.