TB PREVALENCE SURVEY
A POPULATION-BASED TUBERCULOSIS PREVALENCE SURVEY IN ZIMBABWE
Funder: Global Fund Against AIDS, TB, and Malaria through the Ministry of Health and Child Welfare
Award Period: 2 years
Principal Investigator: Dr Charles Sandy ( Ministry of Health and Child Welfare SR)
Co-Principal Investigator : Mrs J Mutsvangwa ( Biomedical Research and Training Institute SSR )
Survey Coordinator: Ronnie Matambo ( SSR )
To determine the national prevalence of bacteriologically confirmed pulmonary TB in Zimbabwean population aged ≥15years within the period 2013/ 2014
Specific Survey Objectives
• To establish the prevalence of bacteriologically-confirmed pulmonary TB in the target population.
• To determine the prevalence of smear positive, culture positive TB
• To determine the prevalence of symptoms suggestive of TB
• To determine the prevalence of radiological abnormalities (chest X-ray) suggestive of TB
Tuberculosis is a significant public health problem in Zimbabwe with high morbidity and mortality rates. According to WHO Global Tuberculosis Report 2012, the estimated TB incidence in 2011 was 603 cases per 100,000 population. In the same year, the estimated prevalence of TB (all forms) in Zimbabwe was 547 cases per 100,000 population. The case notification rate for all TB cases in 2011 was 318 per 100 000 population. This notification rate shows a case detection rate of 53% compared to the estimated TB burden.
Tuberculosis prevalence is one of the indicators of MDGs to the Global Stop TB Plan. Therefore, there is need for countries with high TB burden to have accurate estimates of TB prevalence in order to monitor their progress towards the MDGs. In Zimbabwe, the number of patients notified is not showing a smooth trend over several years and this may be due to inconsistent recording and reporting of the cases. Therefore, estimates from the national TB program may not provide accurate estimates of TB prevalence and incidence. Thus, the true epidemiology of the disease remains unknown. The TB prevalence survey to be conducted will serve as a baseline for future surveys and will assist the programme in planning interventions.
A nationally representative, cluster-sampled, stratified, cross-sectional survey, will be conducted in 2013 over an eight-month period. Enumeration areas (referred to as cluster) will be used as the sampling unit. Enumeration areas (EAs) are smaller in population size and have an average adult population size of 200. Therefore three EAs will be combined to become one cluster with an average population of 600 adults.
For a nationally-representative sample to be drawn, the clusters will be sub-divided in two strata, urban (29%) and rural (71%). Multistage cluster sampling will be performed to select the clusters using probability proportional to size (PPS) ..
The survey will be conducted on a population aged ≥ 15 years that meet the eligibility criteria. All study participants will be screened for TB suggestive symptoms by individual interviews and chest X-ray (CXR). Individuals who will have undergone the initial screening and are found to have symptoms suggestive of TB and/or have an abnormal CXR will be asked to submit two sputum samples.. All sputum samples will be sent to the National Microbiology Reference Laboratory(NMRL)and examined with both microscopy and culture for acid fast bacilli. Prevalent TB cases will be identified based on results of bacteriological examination (smear and culture ).