Incidence of Smear-positive Tuberculosis in Dale District, Sidama, South Ethiopia

Background: Estimating TB incidence rate using follow-up study has not been done in southern Ethiopia. Objective: The aim of this study was to estimate incidence rate of smear-positive TB in Dale district, Sidama Region, South Ethiopia. Methods: In a cohort study conducted among 36,575 people in six rural communities: 14,801 children, 92 cases with history of TB treatment and 15 smear-positive TB cases were excluded from the cohort. For 648 smear-negative patients with symptoms of TB and 1443 neighbourhood controls, we did a 3 – 4 monthly follow-up surveys and detected TB cases. For the rest of population, at the end of the follow-up, identification of TB cases from the district TB register was done. Results: In this study, 21,667 adult people were followed for 18,031 person-years and detected 49 new TB cases. Incidence rate of smear-positive TB was (273; 95% CI: 206 – 361)/100,000 person-years. The risk of smear-positive TB was higher among illiterate people (Adjusted incidence rate ratio 2.4; 95% CI 1.2 – 5.0). Conclusion: TB continued to be a major public health problem in rural communities of South Ethiopia. A high incidence rate of smear-positive TB was observed in the study settings. To improve specificity of the diagnosis, future studies should consider using sputum culture or GeneXpert in screening and diagnosis of TB.