Title:
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Prevalence of latent tuberculosis infection in Sudan: A case-control study comparing interferon-γ release assay and tuberculin skin test |
Author:
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Khalil, Eltahir Awad G; Musa, Ahmed M.; Salih, Kawthar Abd Eljalil Mohamed
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Abstract:
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Most people exposed to M. tuberculosis show no evidence of clinical disease. Five to 10% of
individuals with latent infection progress to develop overt disease during their life time. Identification of people
with latent TB infection will increase case detection rates and may dictate new treatment policies to control
tuberculosis. This study aimed to determine LTBI point prevalence in a population from Sudan using two different
diagnostic methods: the tuberculin skin test (TST) and the IFN-γ release assay (IGRA).
Methods: This was a prospective, community-based and case-controlled study. Following informed consent,
household contacts (HHCs; n = 98) of smear-positive index cases and Community controls (CCs; 186), were enrolled.
Tuberculin skin test (TST), whole blood stimulation with ESAT-6/CFP-10 ± TB7.7 antigens or purified protein
derivative (PPD) and IFN-γ levels determination with ELISA were performed. The levels of IFN-γ and TST induration
between the CCs and the HHCs were compared using student t-test, Chi-square and Kappa coefficient. Pearson
correlation test was used to compare TST and IFN-γ. P levels of <0.05 were considered significant.
Results: TST induration of ≥ 10 mm gave an LTBI point prevalence of 327 cases/1000 individuals among HHCs
compared to 126 cases/1000 individuals among CCs (p = 0.000). PPD-induced IFN-γ release assay gave an LTBI point
prevalence of 418 cases/1000 individuals among HHCs compared to 301 cases/1000 individuals among CCs
(p =0.06). On the other hand ESAT-6/CFP-10 ± TB7.7-induced IFN-γ gave an LTBI point prevalence of 429 cases/1000
individuals among HHCs compared to 268 cases/1000 individuals among CCs (p = 0.01). IFN-γ productions levels
induced by ESAT-6/CPF-10 ± TB7.7 antigens in HHCS and CCs were not significantly different from those induced by
PPD (p = 0.7).
Conclusion: IFN-γ release assay (IGRA) gave higher LTBI point prevalence compared to TST in HHCs and CCs. PPD
gave comparable results to ESAT-6/CFP-10 ± TB7.7 antigens in whole blood IFN-γ release, making it a cheap
alternative to the recombinant antigens. |
URI:
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http://khartoumspace.uofk.edu/123456789/17025
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Date:
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2015-11-12 |