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P167. How frequent are conversions of tuberculosis (TBC) screening tests among inflammatory bowel disease (IBD) patients under anti‑TNF treatment?

F. Bermejo1, A. Algaba1, M. Chaparro2, C. Taxonera3, A. López-Sanromán4, I. Guerra1, J.P. Gisbert2, D. Olivares3, E. Garrido4, G. De la Poza1, I. García-Arata5

1Hospital Universitario de Fuenlabrada, Gastroenterology, Fuenlabrada, Spain; 2Hospital Universitario de La Princesa-IP, Gastroenterology and CIBERHED, Madrid, Spain; 3Hospital Clinico Madrid, IBD Unit; Gastroenterology Division, Madrid, Spain; 4Hospital Universitario Ramón y Cajal, Gastroenterology, Madrid, Spain; 5Hospital Universitario de Fuenlabrada, Laboratory, Fuenlabrada, Spain

Background: Tuberculosis (TBC) reactivation can lead to severe complications in patients treated with anti-TNF. The rate of conversion of tuberculosis screening tests among IBD patients under these drugs is not well known. The usefulness of repeating TBC screening tests in IBD patients under anti‑TNF has not been established.

Our aim was to know the PPD conversion rate in IBD patients under anti‑TNF therapy. Aim: to evaluate the correlation between PPD and Quantiferon® test in these patients.

Methods: Cross-sectional study in IBD patients under anti‑TNF treatment during at least 12 months. In all cases the evaluations recommended for the screening of latent TBC infection prior to the initiation of the anti‑TNF drug had been negative. A blood sample was obtained from each patient to perform the Quantiferon-TB Gold In-tube (Cellestis®) and, after that, 2 units of PPD following the Mantoux intradermal method were administered; the skin reaction was evaluated 72 h later. PPD conversion was defined as skin induration ≥5 mm.

Results: 67 patients were included (mean age 41±12 years, 55% women). The booster of the Mantoux had been performed in 67% of patients (who were under inmunomodulators) before the initiation of anti‑TNF drugs. At the time of the inclusion in this study, the median duration of anti‑TNF treatment was 39 months (IQR 21–55), 44 patients on infliximab, 23 on adalimumab, 19% of the patients were receiving an intensified dose, and 15% of them had received another anti‑TNF before. 33% of patients were on concomitant treatment with thiopurines, 6% with methotrexate and no patient was on steroids. There was history of previous BCG vaccination in 9% of the patients, risk of exposure at work in 6%, and travel to areas of high prevalence in 1.5%. The cumulative incidence of PPD conversion was 3% (n = 2), and the incidence rate of PPD conversion was 0.9% per patient-years of treatment with anti‑TNF drugs. In the two patients with positive skin test, the chest x‑ray was normal and they did not have symptoms suggestive of TBC. All Quantiferon tests but one (a patient with an indeterminate result and a negative PPD) were negative. Chemoprophylaxis with isoniazid was administered to the patients with positive PPD.

Conclusions: The incidence rate of conversion of tuberculosis screening tests among IBD patients under anti‑TNF treatment seems to be lower than that previously reported. These conversions were diagnosed based on a positive PPD, while Quantiferon was negative in all of them.