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* = Presenting author

P244 Performance of Tuberculin skin test in routine screening for latent tuberculosis infection in patients with inflammatory bowel diseases

C. Taxonera*1, 2, A. Ponferrada3, J.P. Gisbert4, F. Bermejo5, M.D. Martínez-Arranz6, M.L. de Castro7, P. López-Serrano8, M.I. Vera9, V. García-Sánchez10, A. Hernandez-Camba11, G. Bastida12, L. Fernandez-Salazar13, O. Merino14, R. Gómez15, D. Ceballos16, I. Morales17, C. Alba1, 2, D. Olivares1, 2, S. Riestra18

1Hospital Clínico San Carlos, IBD Unit, Madrid, Spain, 2Hospital Clínico San Carlos, IdISSC, Madrid, Spain, 3Hospital Infanta Leonor, Gastroenterology, Madrid, Spain, 4Hospital La Princesa , IP and CIBERehd, Gastroenterology Unit, Madrid, Spain, 5Hospital de Fuenlabrada, Gastroenterology, Madrid, Spain, 6University Hospital La Paz, Gastroenterology, Madrid, Spain, 7Complejo Hospitalario Universitario de Vigo, Gastroenterology, Vigo, Spain, 8Hospital Universitario Fundación Alcorcón, Gastroenterology, Madrid, Spain, 9Hospital Puerta de Hierro, Gastroenterology, Madrid, Spain, 10Hospital Reina Sofía, Gastroenterology, Córdoba, Spain, 11Hospital Universitario de Canarias, Gastroenterology, La Laguna, Spain, 12Hospital La Fe, Gastroenterology, Valencia, Spain, 13Hospital Clínico de Valladolid, Gastroenterology, Valladolid, Spain, 14Hospital de Cruces, Gastroenterology, Bilbao, Spain, 15Hospital Virgen de las Nieves, Gastroenterology, Granada, Spain, 16Hospital Dr. Negrín, Gastroenterology, Las Palmas de Gran Canaria, Spain, 17Hospital de Alcalá, Gastroenterology, Madrid, Spain, 18Hospital Central de Asturias, Gastroenterology, Oviedo, Spain

Background

Screening for latent tuberculosis infection (LTBI) before starting therapy with anti tumor necrosis factor (anti-TNF) antibodies has decreased the risk of active tuberculosis. Corticosteroids (CS) or immunosuppressive (IS) therapy may affect the performance of the Tuberculin skin test (TST). The aim of this study was to determine the likelihood of detecting LTBI using a 2-step TST in two cohorts of patients with inflammatory bowel diseases: candidates and non-candidates for anti-TNF therapy. We also analyzed factors associated with the performance of the TST.

Methods

This prospective multicenter case-control study included 240 consecutive patients selected for anti-TNF therapy and 326 controls. LTBI risk factors were recorded and patients underwent chest X-ray and 2-step TST. TST was considered positive if induration was ≥ 5 mm in the first or the second (booster) test. Factors associated with TST Results were analyzed by logistic regression.

Results

Ninety-three of 566 patients (16.4%) had a positive TST (21/93 [22.6%] in the second test). Twenty-three of 240 (9.6%) patients in the anti-TNF group and 70 of 326 (21.5%) in the control group had a positive TST (odds ratio [OR] 0.39; 95% confidence interval [CI] 0.23-0.64; p<0.001). The proportion of Crohn´s disease patients was higher in the anti-TNF group (169/240 [70.7%] vs. 180/326 [56.3%]; p=0.002). More anti-TNF group patients were receiving CS therapy (37.6% vs. 28.5%; p=0.023), IS therapy (64.6% vs. 34.6%; p<0.001), or CS+IS therapy (21.5% vs. 12.5%; p<0.001). The proportion of patients who had normal C-reactive protein (CRP) was lower in the anti-TNF group (38.3%) compared to the control group (64.5%; p<0.001). In the univariate analysis, positive TST was associated with age, Bacille Calmette-Guerin vaccination and mesalazine therapy. Negative TST was associated with CS therapy, IS therapy, CS+IS therapy, Crohn´s disease vs. ulcerative colitis, anti-TNF group vs. control group and elevated CRP. In the multivariate analysis, positive TST was associated with age while negative TST was associated with CS therapy (OR 0.32; 95% CI 0.15-0.70; p=0.004), IS therapy (OR 0.34; 95% CI 0.18-0.61; p<0.001) or CS+IS therapy (OR 0.16; 95% CI 0.06-0.40; p<0.001).

Conclusion

CS and IM therapy strongly negatively affected TST performance. As a result the likelihood of having a positive TST was lower in patients candidates for anti-TNF therapy than in controls. Therefore, current guidelines for TB screening prior to anti-TNF therapy appear inaccurate in patients under CS or IS. Patients should be screened for LTBI prior to initiation of CS or IS therapy. The second TST is useful because it increases detection sensitivity by 22%.