What is the screening test of TB?

Tuberculin skin testing (mantoux test PPD) Injection of a dose of PPD into skin, and see mantoux reaction, three classifications: low risk (minimal exposure, no known hx of exposure, considered positive if 15mm cut off point) Intermediate risk (residents of TB endemic countries, microbiologists..., positive if induration 10mm) High risk (HIV +, previous TB evidence, contact with pt, positive if induration 5 mm) It indicates exposure or latent TB, but not specific (needs CXR confirmatory, and may give false positive (if exposed to BCG vaccine)