| Tuberculosis (TB) affects 8 million people and causes 2 million deaths annually. Models of the global TB epidemic predict that this burden will decrease if at least 70% of new sputum-smear positive pulmonary TB cases are detected and, of these, at least 85% are cured with adequate chemotherapy. The WHO has therefore set these thresholds as targets for its DOTS global TB control strategy. Thus far, Vietnam is the only high-burden country that has reported case detection rates (CDR) and cure rates (CR) well above these targets over several years, and the first country where the impact of the global DOTS strategy on the TB burden can be evaluated. Recent surveys found no consistent evidence for such impact. This either means that DOTS with the current targets does not work in all settings, or that the true CDR and CR are lower than reported in the Vietnamese National TB Control Program (NTP). The latter seems possible since the way these indicators are estimated partly depend on program performance. As part of a larger project to study the impact of the DOTS strategy on the TB burden in Vietnam, this PhD project aims at estimating the CDR and CR of pulmonary TB achieved by the NTP by methods that are independent of its performance. The CDR is estimated directly by measuring the prevalence of TB in a nation-wide survey of 100,000 adults in 70 randomly selected population clusters by microscopic examination and culture of sputum samples of suspects identified by chest X-ray screening or symptoms. The incidence of TB will be estimated from this prevalence and from additional data on diagnostic delay and compared with the TB case notification rate. Inadequate CR result in an increasing proportion of TB patients with primary drug resistance. Drug resistance will be assessed through a nation-wide drug susceptibility testing (DST) survey among 2100 new smear-positive TB patients diagnosed at 80 randomly selected TB clinics and compared with a previous survey. Risk factors for (multidrug) resistance will be studied to identify flaws in treatment and reporting. The project is developed and implemented within the framework of a long-term research collaboration with the explicit objectives of doing demand-driven epidemiological and operational research to inform and guide the NTP's TB control policies, and to build and strengthen the its capacity to do such research. |
