Demographic risk factors for extra-pulmonary tuberculosis: a rising public health threat in Bhutan

Background: Recently, extra-pulmonary tuberculosis (EPTB) has been increasingly reported in Bhutan, rising from 26% in 2001 to 39% in 2010. In 2016, almost half (49%) of all reported TB cases were classified as EPTB. Thus, this study was conducted to understand the epidemiology and identify risk factors contributing to increasing notification of EPTB in Bhutan.

Methods: A case-control study was conducted by recruiting all 110 cases of nationally notified EPTB (Extrapulmonary bacteriologically confirmed/EPBC) as cases and 235 Pulmonary TB (Pulmonary bacteriologically confirmed/PBC) as controls. Data were collected on socio-demography, clinical and diagnostic, behavioral and lifestyle and environmental exposures using a structured questionnaire between April and September, 2018.

Results: The median age of the cases was 25 years, ranged 9-79 years. Lymphatic TB was predominant (n = 78; 70.91%) followed by genitourinary TB (n = 4 (3.64%). The likelihood of EPTB decreased with increase in age (p = 0.023). The odds of EPTB in females was 1.65 times higher than the males (p = 0.038). Increase in Body Mass Index (adjusted odds ratio (AOR): 1.1; 95% confidence interval (CI): 1.052-1.200) and urban residency were (AOR 1.6; 95% CI 1.016-2.805) were found to have higher odds of developing EPTB.

Conclusion: Females, urban residents, and those with higher BMI are at increased risk of developing EPTB. These at-risk groups can be used to target limited public health resources to control EPTB in Bhutan.