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P391 Are cut-off ranges of Infliximab serum levels in Crohn’s disease always the same in clinical practice?

T. Valdes Delgado1, M. Guerra Veloz*1, M. Belvis Jimenez1, B. Maldonado Pérez1, L. Castro Laria1, A. Benítez Roldán1, R. Perea Amarillo1, V. Merino Bohorquez2, M. A. Calleja Hernandez2, T. Ortiz3, A. Caunedo Álvarez1, A. Vilches Arenas4, A. Saez Diaz5, F. Argüelles-Arias1

1Virgen Macarena Hospital, Gastroenterology, Seville, Spain, 2Virgen Macarena Hospital, Pharmacy Unit, Seville, Spain, 3University of Seville, Seville, Spain, 4Virgen Macarena Hospital, Preventive Medicine and Public Health, Seville, Spain, 5Virgen Macarena Hospital, Statistics, Seville, Spain


It has been seen that 30–40% of patients treated with Infliximab (IFX) who achieve an initial response to induction therapy lose this response over time with maintenance treatment. Therapeutic drug monitoring (TDM) could be used to optimise management in such situations. However, IFX serum levels are not well defined. The aim of the study was to find our cut-off range of Infliximab serum levels in Crohn’s disease (CD) patients in remission in clinical practice.


An observational retrospective study was developed from 1 February 2016, to 30 November 2017, in our hospital. Patients with established CD who had been on maintenance dosing schedule of IFX were included. IFX and antibody to IFX levels were measured before each infusion at least twice and after 6 months of treatment in all patients. All the tests were performed using enzyme linked immunosorbent assay (ELISA) with Progenika kits (PROMONITOR®). Clinical remission was defined using Harvey–Bradshaw Index (HBI ≤ 4). The interpretation of data was by cluster analysis (Silhouette measure of cohesion and separation: cluster quality >0.51).


105 CD patients were included in the study, 57.1% men, with a mean age of 39 (DE ± 12.9). The median (range) time of the disease was 11 years (7–15). The median (range) time of follow-up was 32 months (22–38). Montreal phenotypes were: 76% A2, 35.2% L2 and 53.3% B1. Perianal disease was present in 51.4%. 265 IFX levels were measured during the follow-up.

Patients who achieved remission had IFX serum levels between 4.26 and 8.26 μg/ml vs. 0.06 and 1.43 μg/ml in patients who did not achieve remission (silhouette 0.72) the first time; and 2.84–7.75 μg/ml vs. 0.05–2.69 μg/ml in patients who achieved remission vs. those who did not achieve remission, respectively the second time (silhouette 0.78) (Figure 1).

Cluster IFX-levels both times.

4.26–7.75 μg/ml were the best cut-off range for remission (Table 1).

IFX-levels range in both times.

We found that perianal disease does not have any influence on IFX serum levels for achieved remission.


In our practice, the best value to predict remission status in patients undergoing IFX TDM was found to be 4–8 μg/ml, which was higher than in other studies.


1. Kaufman L, Rousseeuw PJ. Finding Groups in Data. An Introduction to Cluster Analysis. New York: John Wiley & Sons; 1990. doi:10.1002/9780470316801.