title: Time interval to conversion of interferon-gamma release assay after exposure to tuberculosis.
abstract: The proper interval for repeating an interferon-γ release assay (IGRA) among tuberculosis contacts with initially negative results is unknown. The interval for IGRA conversion after exposure to patients with active pulmonary tuberculosis in an outbreak setting was evaluated. In a platoon of 32 soldiers, four active pulmonary tuberculosis patients, in addition to one index patient, were diagnosed during a contact investigation. For the other 27 contacts, a tuberculin skin test (TST) and QuantiFERON® TB-Gold In-Tube (QFT-GIT) assay were performed. For soldiers with a negative result on the initial QFT-GIT assay, the test was repeated at 2, 4, 8, 14, 18 and 30 weeks until positive conversion occurred. When conversion was identified, the subject was treated for latent tuberculosis infection. Initially, 17 (63.0%) soldiers gave positive QFT-GIT results, whereas 21 (77.8%) showed positive TST results. Among 10 participants with initially negative QFT-GIT results, three showed conversion at 2 weeks, three at 4 weeks and three at 14 weeks. Conversion did not occur during the 30-week observation period in one contact. Based on the tuberculosis exposure time-points among the contacts, IGRA conversion generally occurred 4-7 weeks after exposure, although it could occur as late as 14-22 weeks after exposure.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Armed Forces Capital Hospital, Lung Institute, Seoul National University College of Medicine, 101 Daehangno, Jongno-gu, Seoul, 110-744, Republic of Korea.
authors.forename: S W
authors.initials: SW
authors.lastname: Lee
authors.forename: D K
authors.initials: DK
authors.lastname: Oh
authors.forename: S H
authors.initials: SH
authors.lastname: Lee
authors.forename: H Y
authors.initials: HY
authors.lastname: Kang
authors.forename: C-T
authors.initials: CT
authors.lastname: Lee
authors.forename: J-J
authors.initials: JJ
authors.lastname: Yim
mesh_terms: D006801:Humans; D007159:Immunologic Tests / Q000592:standards*; D015994:Incidence; D007371:Interferon-gamma / Q000276:immunology*; D055985:Latent Tuberculosis / Q000175:diagnosis; D008297:Male; D008889:Military Personnel; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification; D015995:Prevalence; D012907:Smoking / Q000453:epidemiology; D013997:Time Factors; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000453:epidemiology; D055815:Young Adult
chemical_list: D007371:Interferon-gamma