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.