Testing for tuberculosis: The Roles of Tuberculin Skin Tests and Interferon Gamma Release Assays

The identification of latent tuberculosis infection (LTBI) in any individual or population has proven to carry significant importance not only for that person s health but also for the control and eventual elimination of tuberculosis (TB) in the United States Traditionally the tuberculin skin test (TST) has served as the standard of care for the identification of prior exposure to Mycobactenum tuberculosis (MTB) However, the specificity of a positive test is less than optimal It is either due to previous vaccination intended to prevent TB or infection with nontuberculous mycobacterium (NTM) Newer tests classified as interferon gamma release assays (IGRA) possess potential advantages over the TST when used for identifying those with MTB infection 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 A propos this experience, we discuss the beneficial role of IGRAs and review the literature on infection with M interjectum