Use of the QuantiFERON®-TB Gold in Tube test for screening TB contacts and predictive value for active TB

BACKGROUND: This study estimated the incidence of progression to active tuberculosis (TB) among contacts categorized by QuantiFERON(®)-TB Gold in Tube (QFT-GIT) test results and investigated other risk factors related to progression to TB. METHODS: Contacts of patients with TB were tested using QFT-GIT and were followed up every 6 months at public health centers to detect clinical progression to TB. RESULTS: Analysis of a retrospective cohort revealed that, of the 625 contacts, 168 were QFT-GIT positive and 457 were negative. Of these, 10 (6%) QFT-GIT-positive and two (0.4%) QFT-GIT-negative contacts progressed to TB during the follow-up period (p < 0.01, statistically significant). Multivariable logistic regression analysis revealed that QFT-GIT positivity (p < 0.01), contact of index patients with many other positive contacts (p < 0.01), household contact (p = 0.014), and untreated latent TB infection (p = 0.047) were independent risk factors for progression to TB during an average follow-up period of 637 days. CONCLUSIONS: Progression to TB among QFT-GIT-positive contacts was higher than among QFT-GIT-negative contacts. Other independent risk factors for progression to TB were index cases with more QFT-GIT-positive contacts as well as household contacts.