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. 2012;7(8):e43520.
doi: 10.1371/journal.pone.0043520. Epub 2012 Aug 24.

Observational study of QuantiFERON®-TB gold in-tube assay in tuberculosis contacts in a low incidence area

Emmanuel Bergot  1 , Eglantine Haustraete, Brigitte Malbruny, Romain Magnier, Marie-Anne Salaün, Gérard Zalcman
Affiliations

Observational study of QuantiFERON®-TB gold in-tube assay in tuberculosis contacts in a low incidence area

Emmanuel Bergot et al. PLoS One. 2012.

Abstract

Background: QuantiFERON®-TB Gold in-Tube (QFT) assay is a recently developed test to assess latent tuberculosis infection in contagious tuberculosis (TB) contact subjects. To assess the QFT assay in recently exposed contacts of active tuberculosis patients in a French area with low TB incidence but high Bacille Calmette-Guerin coverage, and evaluate progression rates to TB disease.

Methodology/principal findings: Between January 2007 and December 2009, 687 contacts of culture-confirmed tuberculosis cases underwent the QFT assay, with tuberculin skin test (TST) in 473, and a 34 months mean follow-up. Of 687 contacts, 148 were QFT positive, while 526 were negative and 13 indeterminate. QFT was positive in 35% of individuals with TST ≥ 10 mm, 47.5% with TST ≥ 15 mm or phlyctenular, but in 21% of cases in which two-step TST (M0 and M3) remained negative. Conversely, QFT was negative in 69% of cases with two-step TST showing conversion from negative to positive. All indeterminate QFT were associated with TST induration <10 mm in diameter. For 29 QFT-positive subjects, no chemoprophylaxis was given due to medical contraindications. Of the remaining 119 QFT-positive contacts, 97 accepted chemoprophylaxis (81.5%), and 79 (81.4%) completed the treatment. Two contacts progressed to TB disease: one subject was QFT positive and had declined chemoprophylaxis, while the other one was QFT negative. QFT positive predictive value for progression to TB was 1.96% (1/51) with a 99.8% (525/526) negative predictive value.

Conclusions/significance: Our results confirm the safety of the QFT-based strategy for assessing the TB chemoprophylaxis indication, as only one contact developed TB disease out of 526 QFT-negative subjects.

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Conflict of interest statement

Competing Interests: Dr. E. Bergot had three non-financially supported presentations for Cellestis scientific symposia, organized during French 2009 Annual Meeting of Pulmonology (CPLF), French 2009 Annual Meeting of Infectiology (JNI), and Specific French Cellestis meeting in Paris (2010). He also received partial financial compensation from Cellestis, for travel and accomodation for attending May 2009 International Meeting on IGRAs at Dubrovnik (Croatia). This does not alter the authors' adherence to all the PLoS ONE policies on sharing data and materials. No other competing interest for the other authors.

Figures

Figure 1
Figure 1. Flow chart of the study population.
QFT: QuantiFERON®-TB Gold in-tube; TST: tuberculin skin test; M: month.
Figure 2
Figure 2. Concordance of QuantiFERON-TB® Gold in-tube (QFT) per tuberculin skin test (TST).
QFT: QuantiFERON®-TB Gold in-tube; TST: tuberculin skin test; P: phlyctenular; M: month. *Three patients with 10–14 mm and phlyctenular TST.
See this image and copyright information in PMC

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