Predictive value for progression to tuberculosis by IGRA and TST in immigrant contacts

The authors determined the positive predictive value (PPV) for progression to tuberculosis (TB) of two interferon-gamma release assays (IGRAs), QuantiFERON-TB (R) Gold In-tube (QFT-GIT) and T-SPOT. TB (R), and the tuberculin skin test (TST) in immigrants contacts. Immigrant close contacts of sputum smear-positive TB patients were included when aged >= 16 yrs and their TST result was >= 5 mm 0 or 3 months after diagnosis of the index patient. Contacts were followed for the next 2 yrs for development of TB disease. Of 339 immigrant contacts with TST >= 5 mm, 324 and 299 had valid results of QFT-GIT and T-SPOT. TB (R), respectively. Nine contacts developed active TB. One patient had not been tested with TST, while another patient had not been tested with QFT-GIT and T-SPOT. TB (R). The PPV for progression to TB during this period was 9/288=3.1% (95% CI 1.3-5.0%) for TST >= 10 mm, 7/184=3.8% (95% CI 1.7-5.9%) for TST >= 15 mm, 5/178=2.8% (95% CI 1.0-4.6%) for QFT-GIT and 6/181=3.3% (95% CI 1.3-5.3%) for T-SPOT. TB (R). Sensitivity was 100%, 88%, 63% and 75%, respectively. The predictive values of QFT-GIT, T-SPOT. TB (R) and TST for progression to TB disease among immigrant close contacts were comparable