There are two major types of tests for identification of TB infection: the tuberculin skin test (TST) and the interferon-gamma release assay (IGRA) blood test. (IGRA does not give false-positive results because of prior BCG vaccination. IGRA test results are available within 24 hours at the earliest

The TST can give false-positive . This may be due to nontuberculous mycobacteria infection and Bacillus Calmette-Guérin (BCG) vaccination.

The TST consists of intradermal injection of tuberculin material, which stimulates a delayed-type hypersensitivity response mediated by T lymphocytes and, in patients with prior mycobacterial exposure, causes induration at the injection site within 48 to 72 hours.