National Survey of Tuberculosis Prevalence in Viet Nam/Enquete Nationale Sur la Prevalence De la Tuberculose Au Viet Nam/Encuesta Nacional Sobre la Prevalencia De Tuberculosis En Viet Nam

Introduction Tuberculosis is still a major cause of morbidity and mortality worldwide. In 2006, an estimated 9.2 million new tuberculosis cases occurred, resulting in 1.7 million deaths. (1) The Viet Nam National Tuberculosis Control Programme (NTP) is based on the principles of DOTS, the core control strategy recommended by the World Health Organization (WHO). (2) According to WHO estimates, since 1997 Viet Nam has reached and exceeded the global targets for tuberculosis control, (2,3) i.e. to detect > 70% of new smear-positive pulmonary tuberculosis cases and cure > 85% of these detected cases. (1) If these targets were met, tuberculosis incidence in Viet Nam would predictably decrease over the period 1997-2004 by 44%. (3,4) Although there was indeed a small decrease in tuberculosis notification rates among women and persons older than 35 years, this was offset by an increase among young men, which led to stabilization in notification rates during this period. (3) In 2006, WHO estimated that Viet Nam ranked 12th among the tuberculosis high-burden countries (1), with a prevalence of smear-positive tuberculosis of 89 per 100 000 population. (WHO, unpublished data, 2008). A major question for the Viet Nam NTP is whether these estimates are correct. However, the tuberculosis burden and case detection rate are unknown, because they can only be measured directly if the incidence is known. Tuberculosis incidence is difficult to measure, but tuberculosis prevalence can be assessed by cross-sectional surveys and can be used to estimate the rate at which tuberculosis patients are detected and put on treatment as part of a tuberculosis control programme (i.e. the patient diagnostic rate, PDR). (5,6) The PDR provides information about the burden of tuberculosis and, if determined ar different times, can show the impact of tuberculosis control measures. We aimed to measure the burden of tuberculosis disease, as revealed by a nationwide representative cross-sectional survey, by estimating the tuberculosis prevalence in Viet Nam and comparing this to the tuberculosis prevalence estimated by WHO (1). We also identified the major demographic determinants of tuberculosis prevalence. Methods Study setting and population We did a population-based cross-sectional survey based on multistage cluster sampling, stratified by urban, rural and remote areas. A sample size of approximately 105 000 adults (15 years or older) was calculated based on 95% confidence interval (CI) boundaries of 71 and 129 per 100 000 for an observed prevalence of 100 per 100 000 population (1) and a design effect factor due to cluster sampling of 1.5. (7) Clusters had an approximate population size of 2240 inhabitants (1500 adults), and 70 clusters were selected. Districts were selected with sampling probability proportional to the population in the 1999 census (General Statistics Office of Vietnam, unpublished data, 2002). In the selected districts, communes and sub-communes were selected by simple random sampling. Briefly, all communes or sub-communes were assigned a random number and in each district one was selected and used as the starting point. Other sub-communes were added until the required number of inhabitants (2240 people) was obtained by first going north from the selected sub-commune and then adding sub-communes along a clockwise route. Smear-positive tuberculosis is usually rare in people younger than 15 years, and it is difficult to collect sputum samples from children. Therefore the population eligible for the survey included all residents aged [greater than or equal to] 15 years in the selected clusters who were present during the survey census. A resident was defined as a person who had lived in the household concerned for at least 3 months. To avoid participation bias, short-term guests in households were excluded from the survey. Measurements The survey was conducted from September 2006 to July 2007. …