• Cell counts and biochemistry on fluid specimens • ADA on fluid from pleural TB, meningitis, peritoneal, or pericardial TB • Free IFN-γ on fluid from suspected pleural or peritoneal TB • Smear microscopy for suspected extrapulmonary TB • NAAT from sites of extrapulmonary TB • Histological examination. The gene discussed is IFNG; the disease is meningitis.