Diagnosis of latent tuberculosis infection

In 2015, there were a total of 9,563 tuberculosis (TB) cases reported in the United States, corresponding to an overall TB incidence of 3.0 cases per 100,000, unchanged compared to the rates for 2013 and 2014. With this trend, the progress toward TB elimination in the United States appears to have stalled after 2 decades of decline. Foreign-born persons and racial/ethnic minorities continued to have TB disease disproportionate to their respective populations (¹). This is a trend observed in the United States and other industrialized nations with a low incidence of TB. In these countries, most new, active cases have occurred among persons who were once infected, contained the infection, and then later developed active disease (²). Resuming declines in TB incidence in the United States will require that more emphasis be placed on strengthening systems for detecting and treating latent TB infection (LTBI) as well as accelerating TB care globally. This chapter reviews the tuberculin skin test (TST) and blood assays to detect LTBI.