Letter: supporting Austrian guidelines on latent tuberculosis screening

evidence that the majority of IBD patients on anti-TNF therapy who initially test positive with an IGRA assay will continue to test positive after 9 months of isoniazid treatment. These data confirm the findings of previous studies indicating that the IGRA test should not be used to monitor the effect of TB chemoprevention. 3 The study by Papay et al. was conducted in Austria, which has a low incidence of TB. It prompted us to consider whether it is useful and/or cost-effective to perform, in their country, serial testing of patients receiving anti-TNF therapy for latent TB infection and who tested negative at baseline. It does not seem reasonable to perform tuberculin skin test (TST), given that conversions did not receive chemoprophylaxis. In addition, in their series, there was not a single IGRA conversion among the 169 patients who initially tested negative. This finding should be considered in the context of numerous studies that suggest that the sensitivity of IGRAs may be decreased in patients treated with antiTNF-a agents. 5 On the other hand, significant withinsubject IGRA variability has been reported. Considering all the above, the usefulness of IGRAs for serial testing in patients treated with TNF-a inhibitors should be evaluated further. And what about TST? In our country (Spain), with an incidence of active tuberculosis 4 times higher than in Austria, any positive results in the baseline 2-step TST is a strong indication for chemoprophylaxis in patients scheduled for anti-TNF-a therapy. In 3 studies from Spain, 13 patients had a positive conversion in serial TST while receiving TNF-a inhibitors. All the patients received 9 months of isoniazid treatment while continuing anti-TNF-a, and none of them developed active tuberculosis. We do this because in Spain, and despite all preventive actions, new cases of active TB still occur in patients on anti-TNF-a therapy. In conclusion, the national recommendations in one country for the management of latent TB infection in general, and in patients on TNF-a therapy in particular, may not be applicable to another country. ACKNOWLEDGEMENTS Declaration of personal interests: C. Taxonera and J. P. Gisbert have served as speakers, consultants and advisory board members for Abbott and MSD. Declaration of funding interests: C. Taxonera and J. P. Gisbert have received research funding from MSD and Abbott.