Definitions in tuberculosis (TB)
| Latent TB infection | Asymptomatic state of infection with Mycobacterium tuberculosis demonstrated by a response to in vivo or in vitro stimulation by M. tuberculosis antigens as identified by a positive TST or IGRA. Note that these assays cannot distinguish individuals who have cleared their M. tuberculosis infection from those that remain infected. |
| Persistent TB | Asymptomatic, stable quiescent state of infection with M. tuberculosis and with a persistent response upon in vivo or in vitro antigenic stimulation by M. tuberculosis antigens as identified by a positive TST or IGRA. |
| Incipient TB | Asymptomatic, early pre-clinical disease state during which pathology evolves, such as mycobacterial replication or the inflammatory response. During this state clinical signs of the disease, including TB-compatible symptoms, are still absent. Radiological abnormalities or positive microbiological tests may or may not be present. This state may either evolve and lead to symptomatic clinical TB or regress and remain asymptomatic. |
| Clinical TB | Active symptomatic disease state as a result of the mycobacterial inflammation, with presence of TB-compatible signs and symptoms, which can be demonstrated by radiological, pathological and/or microbiological evidence. |
TST: tuberculin skin test; IGRA: interferon-γ release assay.