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Abstract
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.
Acknowledgments
The authors thank the staff of public health centers and hospitals for collecting information for contact investigations.
Declaration of interest: This study was supported by a grant for a ‘study for effective TB control, including a cost-benefit analysis of periodic health examination and BCG’ from the Japanese Ministry of Health, Labor and Welfare (grant no. H24 Shinko Ippan 011). The authors report no conflicts of interest.
