Determinants of QuantiFERON Plus-diagnosed tuberculosis infection in adult Ugandan TB contacts: A cross-sectional study.

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Martineau, Adrian R  ORCID logo
Tiwari, Divya 
Nakiyingi, Lydia 
Kateete, David P 

BACKGROUND: The tuberculin skin test is commonly used to diagnose latent tuberculosis infection (LTBI) in resource-limited settings, but its specificity is limited by factors including cross-reactivity with BCG vaccine and environmental mycobacteria. Interferon-gamma release assays (IGRA) overcome this problem by detecting M. tuberculosis complex-specific responses, but studies to determine risk factors for IGRA-positivity in high TB burden settings are lacking. METHODS: We conducted a cross-sectional study to determine factors associated with a positive IGRA by employing the QuantiFERON-TB® Gold-plus (QFT Plus) assay in a cohort of asymptomatic adult TB contacts in Kampala, Uganda. Multivariate logistic regression analysis with forward stepwise logit function was employed to identify independent correlates of QFT Plus-positivity. RESULTS: Of the 202 participants enrolled, 129/202 (64%) were female, 173/202 (86%) had a BCG scar, and 67/202 (33%) were HIV-infected. Overall, 105/192 (54%, 95% CI 0.48-0.62) participants had a positive QFT Plus result. Increased risk of QFT-Plus positivity was independently associated with casual employment/unemployment vs. non-casual employment (adjusted odds ratio (aOR) 2.18, 95% CI 1.01-4.72), a family vs. non-family relation to the index patient (aOR 2.87, 95% CI 1.33-6.18), living in the same vs. a different house as the index (aOR 3.05, 95% CI 1.28-7.29), a higher body mass index (BMI) (aOR per additional kg/m2 1.09, 95% CI 1.00-1.18) and tobacco smoking vs. not (aOR 2.94, 95% CI 1.00-8.60). HIV infection was not associated with QFT-Plus positivity (aOR 0.91, 95% CI 0.42-1.96). CONCLUSION: Interferon Gamma Release Assay positivity in this study population was lower than previously estimated. Tobacco smoking and BMI were determinants of IGRA positivity that were previously unappreciated.

Humans, Adult, Female, Male, Latent Tuberculosis, Cross-Sectional Studies, Uganda, Tuberculosis, Interferon-gamma Release Tests, Tuberculin Test, HIV Infections
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PLoS One
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Public Library of Science (PLoS)
Wellcome Trust (107742/Z/15/Z)