title: Performance of confirmatory interferon-γ release assays in school TB outbreaks.
abstract: BACKGROUND
  Interferon-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.
  
  
  METHODS
  We 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).
  
  
  RESULTS
  Among 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.
  
  
  CONCLUSIONS
  The 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.
authors: Department of Thoracic and Cardiovascular Surgery, School of Medicine, Pusan National University, Busan, Korea.
authors: Seunghwan
authors: S
authors: Song
authors: Department of Internal Medicine, School of Medicine, Pusan National University, Busan, Korea.
authors: Doosoo
authors: D
authors: Jeon
authors: Department of Thoracic and Cardiovascular Surgery, School of Medicine, Pusan National University, Busan, Korea.
authors: Jong Won
authors: JW
authors: Kim
authors: Department of Thoracic and Cardiovascular Surgery, School of Medicine, Pusan National University, Busan, Korea.
authors: Yeong Dae
authors: YD
authors: Kim
authors: Department of Thoracic and Cardiovascular Surgery, School of Medicine, Pusan National University, Busan, Korea.
authors: Sang-Pil
authors: SP
authors: Kim
authors: Department of Internal Medicine, School of Medicine, Pusan National University, Busan, Korea.
authors: Jeong Su
authors: JS
authors: Cho
authors: Department of Internal Medicine, School of Medicine, Pusan National University, Busan, Korea.
authors: Seung Eun
authors: SE
authors: Lee
authors: Department of Internal Medicine, School of Medicine, Pusan National University, Busan, Korea.
authors: Woo Hyun
authors: WH
authors: Cho
authors: Department of Internal Medicine, School of Medicine, Pusan National University, Busan, Korea.
authors: Hye-Kyung
authors: HK
authors: Park
authors: Department of Internal Medicine, School of Medicine, Pusan National University, Busan, Korea. Electronic address: yskimdr@yahoo.co.kr.
authors: Yun Seong
authors: YS
authors: Kim
authors: Department of Internal Medicine, School of Medicine, Pusan National University, Busan, Korea.
authors: Min Ki
authors: MK
authors: Lee
authors: Department of Emergency Medicine, Samsung Changwon Hospital, Changwon, South Korea.
authors: Jun Ho
authors: JH
authors: Lee
mesh_terms: D000293:Adolescent; D001500:BCG Vaccine; D016358:Contact Tracing; D004196:Disease Outbreaks; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D059425:Interferon-gamma Release Tests; D008297:Male; D056910:Republic of Korea; D012189:Retrospective Studies; D012572:School Health Services; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000635:transmission; D014611:Vaccination
chemical_list: D001500:BCG Vaccine