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

Armauer Hansen Research Institute, Addis Ababa, Ethiopia. .
BMC Research Notes 08/2012; 5(1):415. DOI: 10.1186/1756-0500-5-415
Source: PubMed


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.
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.
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).
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.

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    • "Other studies in the same site reported 59.3% among TB suspects using QFT-GIT assay [41]. A study conducted at Addis Ababa University on male medical students also showed that 43.9% was QFT-GIT positive which is higher than our result [42]. One possible explanation for this might be the immuno-suppressive effect of pregnancy [43]. "
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    ABSTRACT: M. tuberculosis and helminth infection each affects one third of the world population. Helminth infections down regulate cell mediated immune responses and this may contribute to lower efficacy of BCG vaccination and higher prevalence of tuberculosis. To determine the effect of maternal helminth infection on maternal and neonatal immune function and immunity to TB. In this cross sectional study, eighty five pregnant women were screened for parasitic and latent TB infections using Kato-Katz and QFT-GIT tests, respectively. IFN-γ and IL-4 ELISpot on Cord blood Mononuclear Cells, and total IgE and TB specific IgG ELISA on cord blood plasma was performed to investigate the possible effect of maternal helminth and/or latent TB co-infection on maternal and neonatal immune function and immunity to TB. The prevalence of helminth infections in pregnant women was 27% (n = 23), with Schistosoma mansoni the most common helminth species observed (20% of women were infected). Among the total of 85 study participants 25.8% were QFT-GIT positive and 17% had an indeterminate result. The mean total IgE value of cord blood was significantly higher in helminth positive than negative women (0.76 vs 0.47, p = 0.042). Cross placental transfer of TB specific IgG was significantly higher in helminth positive (21.9±7.9) than negative (12.3±5.1), p = 0.002) Latent TB Infection positive participants. The IFN-γ response of CBMCs to ESAT-6/CFP-10 cocktail (50 vs 116, p = 0.018) and PPD (58 vs 123, p = 0.02) was significantly lower in helminth positive than negative participants. There was no significant difference in IL-4 response of CBMCs between helminth negative and positive participants. Maternal helminth infection had a significant association with the IFN-γ response of CBMCs, total IgE and cross placental transfer of TB specific IgG. Therefore, further studies should be conducted to determine the effect of these factors on neonatal immune response to BCG vaccination.
    PLoS ONE 04/2014; 9(4):e93429. DOI:10.1371/journal.pone.0093429 · 3.23 Impact Factor
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    • "On the other hand, a higher TST conversion rate was reported in high-risk groups, living in a suburban area of Ethiopia, though this was at least partly due to BCG vaccination [25]. A very recent report from apparently healthy Ethiopian adults showed a larger proportion of tuberculin reactors [26]. Whether the majority of our participants did not respond to TST because of functionally depressed immune responses or because they were not infected with M. tuberculosis cannot be definitively answered by this study. "
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