Prevalence of asymptomatic pulmonary tuberculosis by bacteriological status and the associated risk factors. A secondary data analysis of the Uganda national tuberculosis prevalence survey, 2014-2015

BackgroundNearly half of people with tuberculosis (TB) in high incidence settings have asymptomatic disease. Analyzing the different types of asymptomatic TB and the risk factors could inform TB policy and programmatic interventions. We determined the prevalence and risk factors for asymptomatic TB in Uganda, a high TB/HIV burdened country.  MethodsWe analyzed secondary data from the national tuberculosis prevalence survey (2014-2015). We defined asymptomatic TB based on the WHO definition: Asymptomatic TB bacteriologically confirmed (aTB-C) and unconfirmed (aTB-U), applying the symptom screen criteria: absence of cough >=2 weeks. We explored two other definitions: absence of cough of any duration, and absence of any TB symptom. Multivariable regression analysis was performed to identify factors associated with asymptomatic TB for each definition.ResultsOf the 41,003 participants data analyzed, 80 (41.9%) had asymptomatic bacteriologically confirmed TB defined as “absence of persistent cough >=2 weeks” while 111 (58.1%) had asymptomatic bacteriologically unconfirmed TB. The prevalence of aTB-C based on “absence of cough >=2 weeks” was 196 (95%CI 157-244) and that of aTB-U was 281 (95%CI 233-338) /100,000 population. Past smoking and urban residence were associated with increased prevalence of aTB-C, while age >55 years and past TB treatment were associated with aTB-U.Conclusion and recommendationsA substantial proportion of the prevalent TB patients in Uganda have asymptomatic TB and the determinants of aTB-C and aTB-U appear different. Targeted approaches in the specified population groups incorporating strategies beyond symptom screening are required for early detection of asymptomatic TB and advance TB control efforts.