Prevalence and Determinants of QuantiFERON-Diagnosed Tuberculosis Infection in 9810 Mongolian Schoolchildren

Abstract

Abstract Background There is controversy regarding the potential influence of vitamin D deficiency, exposure to environmental tobacco smoke, BCG vaccination, season, and body habitus on susceptibility to Mycobacterium tuberculosis (MTB) infection. Methods We conducted a cross-sectional analysis to identify determinants of a positive QuantiFERON-TB Gold (QFT) assay result in children aged 6–13 years attending 18 schools in Ulaanbaatar, Mongolia. Data relating to potential risk factors for MTB infection were collected by questionnaire, physical examination, and determination of serum 25-hydroxyvitamin D (25[OH]D) concentrations. Risk ratios (RRs) were calculated with adjustment for potential confounders, and population attributable fractions (PAFs) were calculated for modifiable risk factors identified. Results Nine hundred forty-six of 9810 (9.6%) participants had a positive QFT result. QFT positivity was independently associated with household exposure to pulmonary tuberculosis (adjusted RR [aRR], 4.75 [95% confidence interval {CI}, 4.13–5.46, P < .001]; PAF, 13.1% [95% CI, 11.1%–15.0%]), vitamin D deficiency (aRR, 1.23 [95% CI, 1.08–1.40], P = .002; PAF, 5.7% [95% CI, 1.9%–9.3%]), exposure to environmental tobacco smoke (1 indoor smoker, aRR, 1.19 [95% CI, 1.04–1.35]; ≥2 indoor smokers, aRR, 1.30 [95% CI, 1.02–1.64]; P for trend = .006; PAF, 7.2% [95% CI, 2.2%–12.0%]), and increasing age (aRR per additional year, 1.14 [95% CI, 1.10–1.19], P < .001). No statistically significant independent association was seen for presence of a BCG scar, season of sampling, or body mass index. Conclusions Vitamin D deficiency and exposure to environmental tobacco smoke are potentially modifiable risk factors for MTB infection.