Tuberculosis Testing LATENT TB • LTBI is diagnosed when an asymptomatic patient has a positive TST or IGRA result with no clinical or radiographic manifestations of active tuberculosis. • The goal of diagnosing and treating LTBI is to decrease the risk for reactivation tuberculosis. • The lifetime risk of developing active infection in patients with LTBI is 5% to 10%. IGRA/QuantiFERON-TB Gold (QFT) • 5 y/o + low or intermediate risk of disease progression • History of BCG vaccination • Unlikely to return to have their TST result interpreted Tuberculin skin testing (TST) False-negative TST result may occur in patients with recent: • Tuberculosis infection • Recent viral infections • Severely immunocompromised (e.g., AIDS) • < 6 years of age ACTIVE TB AFB smear microscopy • Testing three specimens is highly recommended because false-negative results from a single specimen are not uncommon. Mycobacterial culture • Gold standard • Liquid and solid cultures NAAT • Highly recommended to verify the organism if AFB +. • The positive predictive value of a NAAT on a smear-positive sputum sample = 95% • A negative NAAT result cannot be used to exclude pulmonary tuberculosis NAAT + AFB-positive sputum • Improves diagnostic accuracy Extrapulmonary infection • AFB stain • Mycobacterial culture • Histopathology demonstrating caseating granulomas #Tuberculosis #Testing #Diagnosis #Workup #TB #Latent #Active #LatentTB #ActiveTB #InfectiousDiseases
