• Seunghwan Song, Doosoo Jeon, Kim Jong Won JW Department of Thoracic and Cardiovascular Surgery, School of Medicine, Pusan National University, Busan, Korea., Yeong Dae Kim, Sang-Pil Kim, Jeong Su Cho, Seung Eun Lee, Woo Hyun Cho, Hye-Kyung Park, Yun Seong Kim, Min Ki Lee, and Lee Jun Ho JH Department of Emergency Medicine, Samsung Changwon Hospital, Changwon, South Korea..
• Department of Thoracic and Cardiovascular Surgery, School of Medicine, Pusan National University, Busan, Korea.
• Chest. 2012 Apr 1; 141 (4): 983-988.

BackgroundInterferon-γ release assays (IGRAs) have been incorporated into several national guidelines for latent TB infection (LTBI) diagnosis. However, their optimal application is still controversial and evolving. The aim of this study is to evaluate the performance of confirmatory IGRAs in addition to tuberculin skin tests (TSTs) in high school students with TST-positive (TST+) results who have had contact with another student who had TB (referred to in this article as "contacts") in TB outbreaks in a high BCG-vaccinated population.MethodsWe conducted a retrospective observational study of contacts in five school TB outbreaks in South Korea. The progression rates of TB within 2 years were compared among the groups based on the results of TSTs and QuantiFERON-TB gold assays (QFT-Gs).ResultsAmong 1,826 contacts, 21 (1.2%) developed active TB. Of the untreated groups, the rate of progression to TB was higher in the group with TST-positive (TST+) results (6.1%, six of 99) than in that with TST-negative (TST-) results (0.6%, 10 of 1,556; P < .001). Among TST+ contacts, the rate of progression to TB was higher in the group with QFT-G-positive (QFT-G+) results (18.75%, six of 32) than that with QFT-G-negative (QFT-G(-)) results (0%, 0 of 67; P = .001). None of the 67 contacts with TST+/QFT-G(-) results progressed to active TB.ConclusionsThe addition of a confirmatory IGRA for TST+ contacts could effectively focus the targeting of LTBI treatment to fewer contacts in an intermediate-incidence setting in a high BCG-vaccinated population.

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