Abstract
ObjectiveTo 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.MethodsWe 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 resultsSix 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).ConclusionsIn BCG-vaccinated TB contacts, the addition of QFT-GIT safely reduced TB diagnosis and treatment rates without increasing the risk of subsequent active TB.
Highlights
Detection and treatment of recently infected people is an essential measure of tuberculosis (TB) control in low-prevalence countries [1]
By contrast to the TST, the interferon-γ release assays (IGRAs), the in vitro immunodiagnostic tests based on M. tuberculosis complex-specific antigens, have no cross-reactivity with the Bacillus Calmette–Guerin (BCG)-vaccine strains and most non-tuberculous mycobacteria [4,5,6]
The QuantiFERON®-TB Gold In-tube (QFT-GIT) period included a higher proportion of foreign-born individuals (p
Summary
Detection and treatment of recently infected people is an essential measure of tuberculosis (TB) control in low-prevalence countries [1]. A positive TST response indicates infection with Mycobacterium tuberculosis indirectly, by measuring the delayed-type hypersensitivity response to the intradermal injection of a mixture of wall antigens, the socalled PPD (purified protein-derivate), which is shared by many mycobacteria species and the Bacillus Calmette–Guerin (BCG) strain [2]. By contrast to the TST, the interferon-γ release assays (IGRAs), the in vitro immunodiagnostic tests based on M. tuberculosis complex-specific antigens, have no cross-reactivity with the BCG-vaccine strains and most non-tuberculous mycobacteria [4,5,6]. IGRAs yield fewer positive results than TST, are more specific, and have shown a high negative predictive value for better selecting those immunocompetent individuals who will not develop TB; their use for targeting TB contacts for preventive therapy, especially in BCG-vaccinated subjects, may still be preferable to TST and more cost-effective in certain settings [9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
