Zimbabwe to conduct TB national prevalence survey

By Wallace Mawire

Zimbabwe’s Ministry of Health and Child Welfare (MHCW) is to conduct its first national tuberculosis prevalency survey.

The survey, which will cost an estimated US$ 1.7 million from 2013-2016, will be undertaken by Zimbabwe’s Biomedical Research and Training Institute (BRTI) and funded by Global Fund to Fight AIDS, Malaria and Tuberculosis.

According to Dr Charles Sandy, deputy director AIDS/TB Programmes (National TB Control), the main objective of the survey is to determine the national prevalence of bacteriologically-confirmed pulmonary TB among people aged 15 and over.

Other objectives include to determine the prevalence of bacteriologically-confirmed pulmonary TB in a target population  of 12.3 million; to determine the prevalence of smear positive, culture positive TB (which helps to identify the particular mycrobacterium causing the symptoms and gives doctors information on how resistant it may be for treatment); to determine the prevalence of symptoms suggestive of TB and to determine the prevalence of abnormalities in chest X-rays suggestive of TB.

Dr Sandy said the rationale for the survey is that TB is a significant public health problem in Zimbabwe with high morbidity and mortality rates.

The World Health Organisation’s Global Tuberculosis Control 2011 report estimated TB incidence in Zimbabwe in 2010 to be 633 cases per 100,000 people. In the same year, the estimated prevalence of all forms of TB was 402 cases per 100,000 people. The treatment success rate for smear positive cases reported in 2009 falls short of the target of 87% set by the World Health Organisation’s Stop TB Strategy, which Zimbabwe has adopted. Low treatment and cure rates pose a great risk for the development of multi-drug resistant TB (MDR).

“Tuberculosis prevalence is one of the indicators of MDGs [millennium development goals] 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,” Dr Sandy said.

Dr Sandy added that in Zimbabwe the number of registered TB patients has been fluctuating between 42,000 and 47,000. This may be due to inconsistent recording and reporting of the cases. Therefore, estimates from the national TB programme may not provide accurate estimates of TB prevalence and incidence. Thus, the true epidemiology of the disease remains unknown.

Many countries among the 22 carrying the highest TB burdens have conducted at least one prevalence survey, although this will be Zimbabwe’s first.

In addition to monitoring global progress towards the MDGs and the eradication of TB, accurate estimates on TB prevalence and incidence are essential to monitor the national TB programme performance. Dr Sandy argues, given the dire consequences that may be caused by the development of drug-resistant TB on the national TB control programme already strained by high HIV prevalence, it is important to carry routine TB surveillance to establish the prevalence and incidence of both non-drug resistant TB and drug-resistant TB.

“There is need for all high TB burden countries to have accurate estimates of TB prevalence in order to monitor the global progress towards the Stop TB Strategy Plan goal of eradicating TB by 2050,” he added.

The survey is expected to provide accurate estimates on TB prevalence, which will serve as baseline data for future prevalence studies and to improve the national TB control programme. In addition, the study will identify risk factors associated with TB and health seeking behaviour of the people living with and thought to have TB. Further, the survey will provide data on the TB reporting system and on the contribution of the private sector in the management and control of TB. It is to be conducted in 2013 over a ten-month period.

The prevalence survey is designed to provide an estimate of prevalence for the population of an entire country. For a nationally representative sample to be drawn, clusters will be subdivided into urban (29%) and rural (71%) for each province. The survey will be conducted in a population aged above 15 that meet the eligibility criteria. All study participants will be screened for TB suggestive symptoms by individual interviews and chest X-ray.

Screened persons with defined TB suggestive symptoms and or abnormal X-rays will be asked to submit two sputum samples for testing. All sputum samples will be sent to the National TB Reference Laboratory for diagnosis.

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