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P367 The availability of infliximab trough levels in IBD patients on maintenance therapy deeply impacts therapeutic decision-making

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 (ITL) have emerged as a promising tool for the management of inflammatory bowel disease (IBD) patients. However, its real usefulness in clinical practice is still controversial.

Methods

Observational study where IBD patients on maintenance IFX therapy were prospectively included from June 2015 to June 2016. At each IFX infusion, patients were visited by their physician and the actual clinical decision (ACD) was taken regarding clinical and biological data (C-reactive protein (CRP) levels). At this time, blood samples for ITL were collected. Our aim was to compare the ACD with the decisions of 3 experts' based on the same data plus the results of ITL (ITL-guided decision –TLGD-). The decisions between experts were also compared. Both comparisons were calculated by the linear Cohen's Kappa (κ) index.

Results

A total of 235 infusions were analyzed among 77 IBD patients. Concordance between ACD and TLGD was poor (κ=0.10 [95% CI: 0.01–0.20]/κ=0.11 [95% CI: 0.01–0.21]/κ=0.10 [95% CI: 0–0.21]) for experts A/B/C. respectively. This “disagreement” was mainly due to a higher proportion of dose-escalations according to the TLGD as compared to the ACD. Among the 215 infusions where no action was taken according to the TD, 85 (40%), 43 (20%) and 59 (28%) patients would have been dose-escalated according to the TLGD for experts A, B and C, respectively. Despite this “disagreement”, most patients remained in clinical and biological remission during the follow up, since only 28% of events were recorded as loss of response defined as clinical relapse and/or CRP ≥5 mg/L. Moreover, concordance between experts was moderate (κ=0.55 [95% CI: 0.41–0.71]/κ=0.40 [95% CI: 0.26–0.55]/κ=0.30 [95% CI: 0.21–0.40]) for experts A-B/B-C/A-C respectively).

Conclusion

ITLs significantly change the therapeutic decision making on IBD patients treated with IFX, mainly towards dose-escalation of IFX. Both the clinical and economical impact of such a potential change in the management of IBD patients needs to be e valuated in future cohorts.