• Jean-Pierre Zellweger, Giovanni Sotgiu, Michael Block, Simone Dore, Neus Altet, Rebecca Blunschi, Matthias Bogyi, Graham Bothamley, Christina Bothe, Luigi Codecasa, Patrizia Costa, Jose Dominguez, Raquel Duarte, Andreas Fløe, Isabelle Fresard, José-María García-García, Delia Goletti, Petra Halm, Doris Hellwig, Eveline Henninger, Helga Heykes-Uden, Liane Horn, Katarzyna Kruczak, Irene Latorre, Geneviève Pache, Heidrun Rath, Felix C Ringshausen, RuizAsunción SeminarioAS, Ivan Solovic, Souza-GalvãoMaria-Luiza deML, Ursula Widmer, Peter Witte, Christoph Lange, and TBNET.
• 1 Swiss Lung Association, Berne, Switzerland.
• Am. J. Respir. Crit. Care Med. 2015 May 15; 191 (10): 1176-84.

RationaleLatent infection with Mycobacterium tuberculosis is defined by a positive IFN-γ release assay (IGRA) result in the absence of active tuberculosis. Only few, mostly monocentric studies have evaluated the role of IGRAs to predict the development of tuberculosis in recent contacts in low-incidence countries of tuberculosis.ObjectivesTo analyze IGRA results and the effect of preventive chemotherapy on tuberculosis progression rates among recent contacts.MethodsResults from contact investigations at 26 centers in 10 European countries including testing for latent infection with M. tuberculosis by the QuantiFERON-TB Gold In-Tube (QFT) test or the T-SPOT.TB (TSPOT) were prospectively collected and analyzed.Measurements And Main ResultsAmong 5,020 contacts of 1,023 index cases, 25 prevalent secondary cases were identified at screening. Twenty-four incident cases occurred among 4,513 contacts during 12,326 years of cumulative follow-up. In those with a positive IGRA result, tuberculosis incidence was 0.2 (QFT) and 0 (TSPOT) per 100 patient-years when contacts received preventive chemotherapy versus 1.2 (QFT) and 0.8 (TSPOT) per 100 patient-years in those not treated (38 and 37 patients needed to be treated to prevent one case, respectively). Positive and negative predictive values were 1.9% (95% confidence interval [CI], 1.1-3.0) and 99.9% (95% CI, 99.7-100) for the QFT and 0.7% (95% CI, 0.1-2.6) and 99.7% (95% CI, 99.1-99.9) for the TSPOT.ConclusionsTuberculosis rarely developed among contacts, and preventive chemotherapy effectively reduced the tuberculosis risk among IGRA-positive contacts. Although the negative predictive value of IGRAs is high, the risk for the development of tuberculosis is poorly predicted by these assays.

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