More unnecessary treatment arising from a suspected false positive TST.

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We recently diagnosed a case of pleuropulmonary infection involving an unusual NTM, Mycobacterium interjectum (M. interjectum), in an immunocompromised man diagnosed 1 year after he had been treated for LTBI based on a reactive TST...

...Familiarity, availability, and low cost account for the current popularity and predominance of the TST for identification of LTBI. The QFT-GIT and T-SPOT assays offer distinct advantages over the TST. Substituting TSTs with IGRAs, as in our patient's case, may prevent patients from receiving unwarranted treatment for LTBI based on false-positive TSTs, either due to prior BCG vaccination or infection with NTM, although no information on the effect of infection with M. interjectum and IGRA test results exists. As knowledge and accessibility of this alternative diagnostic test continue to grow, the clinical practice of how we investigate MTB infection will hopefully evolve in a fashion benefiting the patients we serve.