P510 Skin anergy and latent tuberculosis in inflammatory bowel disease patients
C. Herrera de Guise*, V. Robles, N. Borruel, E. Navarro, F. Casellas
Unitat d’Atenció Crohn-Colitis. Hospital Universitari Vall d’Hebron, Digestive Diseases Research, Barcelona, Spain
Current guidelines recommend screening for latent tuberculosis (LTB) before anti-TNF therapy with tuberculin skin test (TST) or interferon gamma assays (IGRA), detailed history of exposure, and chest radiograph. TST is highly sensitive, but false negatives may occur in anergic patients. Prevalence of anergy in the general population is low (0%–5%), but in immunosuppressed patients, it can increase significantly. We have no information about the prevalence of anergy in inflammatory bowel disease (IBD) patients in our care unit. The aim of our study was to determine the prevalence of anergy in IBD patients before initiation of anti-TNFα agents
We performed an observational, cross-sectional study in IBD patients enrolled in a screening programme before the start of anti-TNFα agents. Standard intradermal test was performed with tuberculin purified protein derivative (PPD), and 2 control skin tests were simultaneously placed (candidin and trichophytin antigen). TST booster test was performed 10 days after the initial test (a second PPD). Demographic and clinical patient data collected, including treatment, dose and duration. Results were expressed as medians, percentages, and percentiles. For categorical variables Fisher’s exact test was performed, and quantitative, Mann–Whitney. A 2-tailed p-value of < 0.05 was considered to be statistically significant.
In total, 130 IBD patients were included in our study. Median age was 37 years [29–48]; 48% were female; and 69% were diagnosed with Crohn’s disease. Median time to disease progression was 60 months [24–144]. Further, 86% of patients were receiving immunomodulators (thiopurines in 87%), and 39 patients were taking corticosteroids (prednisone in 72%). Skin anergy was found in 18 of the 130 patients evaluated (14%). No differences between type of IBD, concomitant immunosuppressive therapy, corticosteroid use, and dosage or duration of the disease were found. IGRA was measured in all patients with skin anergy, and it was negative in all cases. LTB was found in 38 patients, and in 18 cases, it was diagnosed by booster test. Chest radiograph showed no abnormalities in any of the cases of LTB.
Prevalence of skin anergy was 3 times greater in our study group than in the general population. Half of latent TB cases were detected by the booster test. Usefulness of the TST booster test should be further evaluated in patients with IBD.