Directly Observed Therapy, Short-Course: The Best Way to Prevent Multidrug- Resistant Tuberculosis

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Abstract
Adherence to therapy in patients with tuberculosis (TB) is a major determinant of their outcomes. Unfortunately, there are no currently known predictors of adherence, given that this phenomenon represents a complex, task-specific behavior. Notwithstanding criticisms from civil liberty advocates, directly observed therapy (DOT), facilitated by education, holistic care, enablers and incentives, is still the best strategy to ensure patient adherence to treatment. To enhance delivery of DOT, short-course chemotherapy (SCC) must be strongly advocated. Monitoring of patient progress, dependable drug supply, and adequate programme funding are other important elements of the entire strategy. Indeed, since the global resurgence of TB and associated rampant drug resistance in the 1990s, directly observed therapy, short-course (DOTS) has now become the WHO strategy for effective TB control. Data obtained so far in different continents worldwide have underscored the unrivalled efficacy of DOTS in ensuring treatment success and preventing development of acquired drug resistance. The recent WHO/International Union against Tuberculosis and Lung Disease (IUATLD) global project on anti-TB drug resistance surveillance has also revealed that countries in which >33–90% of the population has access to the WHO DOTS strategy have, as a group, lower levels of drug resistance: primary multidrug-resistant (MDR) (1.4%; median) and acquired MDR index (0.6; median). The use of SCC was also inversely associated with the prevalence of combined resistance to any drug. Countries with MDR rates >2% reported using SCC in a median of 70% of their patients, compared with 100% in countries with MDR rates <2% (WHO/TB/97.229). Despite greater initial cost, DOTS is a more cost-effective strategy than self-administered therapy because it decreases the re-treatment costs associated with therapy failure and acquired drug resistance. Finally, in addition to harnessing the complementary roles of a national tuberculosis programme and community participation, DOTS might be further enhanced by the use of newly developed drugs with a long duration of action or more potent bactericidal and sterilizing activities.