Interferon-γ release assay.

Abstract

Traditionally, tuberculosis (TB) has been viewed as having two distinct manifestations, known as TB infection (TBI) and TB disease. The spectrum, however, has recently been expanded to include the elimination of TBI with the help of innate and/or adaptive immunity, TBI, incipient and subclinical TB disease, and TB disease. Epidemiologically speaking, identifying individuals with TBI is critical since diagnosis and treatment of TBI are essential in controlling the TB burden. It is important to identify high-risk individuals with TBI who are more likely to progress to active TB disease. There are two diagnostic methods for identifying TBI. These include the conventional tuberculin skin test (TST) and interferon-γ release assay (IGRA). However, these methods are not the 'gold standard.' Furthermore, all of these methods are indirect, relying on the host's adaptive immune response to Mycobacterium tuberculosis-derived protein antigens. This review will describe the various tests for TBI, such as TST, IGRAs, newer skin and blood tests, methods for performing IGRAs, interpretation strategies, and limitations.