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Latent tuberculosis infection (LTBI) is defined by the presence of detectable immune responses to Mycobacterium tuberculosis antigens with no clinical evidence of active TB disease. 1 It has been estimated that one-quarter of the world population has LTBI; however, there are wide variations in the rates of LTBI across regions. 2 In high-income countries, the incidence of active TB disease has continued to decline over the recent decades, 3, 4 but the prevalence of LTBI has remained stable. For example, in the United

States, 4% to 5% of the population was estimated to have LTBI in 2011 to 2012, 5 similar to prevalence rates reported in 1999 to 2000. 6 This indicates a persistent reservoir of M tuberculosis infection even in countries where active disease is less frequent. Because a majority of new TB cases in these settings are a result of reactivation of remote LTBI rather than recent infection, 7–9 intensification of …