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Open Access Highly Accessed Research article

Diagnosis of latent tuberculosis infection in healthy young adults in a country with high tuberculosis burden and BCG vaccination at birth

Alemnew F Dagnew1237*, Jemal Hussein1, Markos Abebe1, Martha Zewdie1, Adane Mihret12, Ahmed Bedru1, Menberework Chanyalew1, Lawrence Yamuah1, Girmay Medhin4, Peter Bang5, T Mark Doherty56, Asrat Hailu2 and Abraham Aseffa1

Author Affiliations

1 Armauer Hansen Research Institute, Addis Ababa, Ethiopia

2 Department of Microbiology, Immunology and Parasitology, Faculty of Medicine, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia

3 Department of Microbiology, Immunology and Parasitology, College of Health Sciences, Mekelle University, Mekelle, Ethiopia

4 Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia

5 Statens Serum Institut, Copenhagen, Denmark

6 Current address: GSK, Brøndby, Denmark

7 Current address: Global Development, Novartis Vaccines and Diagnostics, Via Fiorentina 1, Siena, 53100, Italy

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BMC Research Notes 2012, 5:415  doi:10.1186/1756-0500-5-415

Published: 7 August 2012

Abstract

Background

One third of the world’s population is thought to have latent tuberculosis infection (LTBI) with the potential for subsequent reactivation of disease. To better characterize this important population, studies comparing Tuberculin Skin Test (TST) and the new interferon-γ release assays including QuantiFERON®-TB Gold In-Tube (QFT-GIT) have been conducted in different parts of the world, but most of these have been in countries with a low incidence of tuberculosis (TB). The aim of this study was therefore to evaluate the use of QFT-GIT assay as compared with TST in the diagnosis of LTBI in Ethiopia, a country with a high burden of TB and routine BCG vaccination at birth.

Methods

Healthy medical and paramedical male students at the Faculty of Medicine, Addis Ababa University, Ethiopia were enrolled into the study from December 2008 to February 2009. The TST and QFTG-IT assay were performed using standard methods.

Results

The mean age of the study participants was 20.9 years. From a total of 107 study participants, 46.7% (95%CI: 37.0% to 56.6%) had a positive TST result (TST≥10 mm), 43.9% (95%CI: 34.3% to 53.9%) had a positive QFT-GIT assay result and 44.9% (95%CI: 35.2% to 54.8%) had BCG scar. There was strong agreement between TST (TST ≥10mm) and QFT-GIT assay (Kappa = 0.83, p value = 0.000).

Conclusion

The TST and QFT-GIT assay show similar efficacy for the diagnosis of LTBI in healthy young adults residing in Ethiopia, a country with high TB incidence.

Keywords:
Tuberculosis; Latent; BCG; Tuberculin skin test; Interferon-γ release assay; Ethiopia