How frequently do tuberculosis screening tests convert in inflammatory bowel disease patients on anti-tumour necrosis factor-alpha? A pilot study.

BACKGROUND: Tuberculosis reactivation can lead to severe complications in patients treated with anti-tumour necrosis factor-alpha.

AIM: To assess the usefulness of repeat tuberculosis screening tests in inflammatory bowel disease patients on stable anti-TNF therapy.

METHODS: Cross-sectional study, in patients on prolonged anti-TNF treatment (≥ 12 months) and basal negative screening for latent tuberculosis. Quantiferon(®)-TB Gold In-tube test was performed and then, tuberculin skin test was administered.

RESULTS: 74 patients were included, median duration of anti-TNF treatment was 30 months (IQR 19-54); 47 patients on infliximab and 27 on adalimumab; no patient was on glucocorticoids. Previous BCG vaccination was present in 5 cases. After anti-TNF was started, 4 patients suffered from potential tuberculosis exposure and two cases travelled to endemic areas. The cumulative incidence of tuberculin skin test conversion was 2.7% (95% CI 0.3-9.4%, 2/74), and the incidence rate of tuberculin skin test conversion was 0.83% (95% CI 0.1-2.9%) per patient-year of treatment with anti-TNF drugs. All Quantiferon tests but one (a patient with an indeterminate result and a negative tuberculin skin test) were negative.

CONCLUSIONS: The incidence rate of conversion of tuberculosis screening tests among patients on anti-TNF treatment seems to be low and these conversions were diagnosed based on a positive tuberculin skin test and were discordant with Quantiferon testing.