Prevalence of pulmonary tuberculosis in adult population of Tanzania: a national survey, 2012.

SETTING

Tanzania is classified as one of the 22 high tuberculosis (TB) burden countries; however, the true burden of TB disease in the country remains unknown.

OBJECTIVE

To assess the prevalence of bacteriologically confirmed pulmonary TB (PTB) in the adult population.

DESIGN

This was a community-based cluster randomised survey with proportional-to-population-size selection of primary sampling units (districts). Participants were screened for TB using a symptom questionnaire and chest X-ray (CXR). Those with abnormal CXR and/or at least one symptom suggestive of TB were classified as individuals with presumptive TB, and asked to submit three sputum specimens for smear microscopy and culture.

RESULTS

The weighted prevalence for sputum smear-positive TB cases was 249 per 100 000 adult population (95%CI 192-305) and that for bacteriologically confirmed TB cases was 293/100 000 (95%CI 228-358). Individuals aged ⩾45 years comprised 55% (71/129) of the identified smear-positive cases, but just 28% (6793/24 648) of the notified TB cases. CXR screening identified more TB cases than symptom screening. When weighted for human immunodeficiency virus prevalence among notified new smear-positive cases, the overall case detection of incident TB cases in 2012 was between 37% and 48%.

CONCLUSIONS

The prevalence of sputum smear-positive PTB and bacteriologically confirmed PTB in the adult population was higher than previous World Health Organization estimates. There is a potential underestimation of the number of bacteriologically confirmed PTB cases in the adult population. The age distribution of prevalent cases suggests an epidemiological shift towards the older generations, which has been a sign of successful TB control activities in the past. However, the survey shows that many infectious TB cases are currently missed by the National Tuberculosis Programme.