FeedbackTesting for M. tuberculosis infection using TST or IGRA is useful to support a diagnosis of TB in children with suggestive clinical features who are sputum smear-negative or who cannot produce sputum. A positive test for TB infection indicates prior or current infection with M. tuberculosis and can be particularly useful in the absence of known TB exposure (no positive contact history), as it confirms the child has been infected at some point in time (6, 15).
TST is considered positive (indicating infection with M. tuberculosis) if:
- it is 10 mm or more in any child, irrespective of BCG immunization;
- it is 5 mm or more in a child living with HIV or a severely malnourished child.
Note that a positive TST or IGRA does not distinguish between TB infection and TB disease.
More details on testing for M. tuberculosis infection are included in Chapter 3 on prevention. Annex 2 provides information on administering, reading and interpreting a TST. Commercial serodiagnostics should not be used in children with presumed pulmonary or EPTB, irrespective of their HIV status (6).