title: QuantiFERON-TB Gold In-Tube test conversions and reversions among tuberculosis patients and their household contacts in Addis Ababa: a one year follow-up study.
abstract: BACKGROUND
  QuantiFERON-TB Gold In-Tube® (QFT-GIT) test is used for the diagnosis of latent tuberculosis (TB) infection. Besides, QFT-GIT test could allow tracking changes in immune response among TB patients and their contacts. In high TB burden settings, reports on QFT-GIT conversions and reversions among TB patients and their contacts are limited. As part of a major project to study immune responses to TB infection, we investigated QFT-GIT test conversions and reversions among smear positive pulmonary TB patients and their household contacts over 12 months.
  
  
  METHODS
  We followed a total of 107 HIV negative participants (33 patients and 74 contacts) in Addis Ababa. We did QFT-GIT test at baseline and 12 months later according to the manufacturer's instructions.
  
  
  RESULTS
  At baseline, 25/33 (75.8%) of the patients and 50/74 (67.6%) of the contacts were QFT-GIT positive. At 12 months, 2 more patients (1 test negative and 1 indeterminate) became test positive. Besides, 11/24 (45.8%) test negative contacts became positive. Only one patient and one contact who were test positive at baseline became test negative 12 months later. At 12 months, the proportions of QFT-GIT test positives for patients and contacts were, therefore, 78.8% and 81.1%, respectively. Among contacts, the proportion of QFT-GIT test positives at 12 months was significantly higher compared to the corresponding proportion at baseline (McNemar, p = 0.006); similarly, the median IFN-γ response significantly increased at 12 months compared with the baseline level (Wilcoxon matched-pairs signed rank test, p = 0.01). Patients, however, had comparable median IFN-γ levels at baseline and 12 months later (p = 0.56).
  
  
  CONCLUSIONS
  Nearly half of QFT-GIT negative household contacts at baseline became positive at 12 months. This suggests that repeated screening of QFT-GIT negative contacts may be needed for epidemiological studies and interventions of latent TB in an endemic setting. A large longitudinal study may be needed to confirm our observations.
authors.affiliation: Aklilu Lemma Institute of Pathobiology, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia. mulg2002@yahoo.com.|Department of Community Medicine, Institute of Health and Society, University of Oslo, P.O. Box 1130, Blindern, 0318, Oslo, Norway. mulg2002@yahoo.com.
authors.forename: Mulugeta
authors.initials: M
authors.lastname: Belay
authors.affiliation: Aklilu Lemma Institute of Pathobiology, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia. mengistu.legessed@aau.edu.et.
authors.forename: Mengistu
authors.initials: M
authors.lastname: Legesse
authors.affiliation: Aklilu Lemma Institute of Pathobiology, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia. danieldagne72@yahoo.com.|Dessie Regional Health Research Laboratory Center, Amhara Regional Health Bureau, P.O. Box 686, Dessie, Ethiopia. danieldagne72@yahoo.com.
authors.forename: Daniel
authors.initials: D
authors.lastname: Dagne
authors.affiliation: Armauer Hansen Research Institute, Addis Ababa, P.O. Box 1005, Ethiopia. adane_mihret@yahoo.com.
authors.forename: Adane
authors.initials: A
authors.lastname: Mihret
authors.affiliation: Armauer Hansen Research Institute, Addis Ababa, P.O. Box 1005, Ethiopia. yoni4m@gmail.com.
authors.forename: Yonas
authors.initials: Y
authors.lastname: Bekele
authors.affiliation: Aklilu Lemma Institute of Pathobiology, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia. gtmedhin@yahoo.com.
authors.forename: Girmay
authors.initials: G
authors.lastname: Medhin
authors.affiliation: Department of Community Medicine, Institute of Health and Society, University of Oslo, P.O. Box 1130, Blindern, 0318, Oslo, Norway. g.a.bjune@medisin.uio.no.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Bjune
authors.affiliation: Department of Community Medicine, Institute of Health and Society, University of Oslo, P.O. Box 1130, Blindern, 0318, Oslo, Norway. fekadu.abebe@medisin.uio.no.
authors.forename: Fekadu
authors.initials: F
authors.lastname: Abebe
mesh_terms: D000328:Adult; D016358:Contact Tracing; D005002:Ethiopia; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D059425:Interferon-gamma Release Tests; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000635:transmission; D008297:Male; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000635:transmission*