Data from: QuantiFERON®-TB Gold In-Tube for contact screening in BCG-vaccinated adults: a longitudinal cohort study

Objective. To assess the utility of QuantiFERON®-TB Gold In-tube (QFT-GIT)
for targeting preventive therapy in BCG-vaccinated contacts of
tuberculosis (TB), based on its high specificity and negative predictive
value for development of TB. Methods. We compared two screening strategies
for TB contact tracing in two consecutive periods: the tuberculin skin
test (TST) period, when all contacts were screened with the TST alone; and
the QFT-GIT period, when BCG-vaccinated contacts underwent TST and
QFT-GIT. Diagnosis of TB infection among BCG-vaccinated contacts relied on
TST ≥5 mm in the TST period, while in the QFT-GIT period either a positive
QFT-GIT or a TST ≥15 mm was required. Measurements and main results. Six
hundred and sixty-one contacts were compared. In the QFT-GIT period there
was a reduction in diagnoses of TB infection (77.4% vs. 51.2%; p
<0.01) and preventive therapy prescribed (62.1% vs. 48.2%; p =
0.02) among the 290 BCG-vaccinated contacts. After a median follow-up of 5
years, cumulative incidences of TB were 0.62 and 0.29 in the TST and
QFT-GIT periods respectively (p = 0.59). Conclusions. In BCG-vaccinated TB
contacts, the addition of QFT-GIT safely reduced TB diagnosis and
treatment rates without increasing the risk of subsequent active TB.