Directly observed therapy effective against drug resistant tuberculosis

Directly observed therapy (DOTS) - the main strategy for tuberculosis control - can rapidly reduce the transmission and incidence of the drug resistant form of the disease, concludes a study published in this week’s issue of The Lancet.

The DOTS strategy for tuberculosis includes a short-course chemotherapy with combinations of first-line drugs. There is growing concern about current and future rates of multidrugresistant (MDR) tuberculosis in the world. Little data exists to guide policy on how to best control and prevent tuberculosis in areas where drug resistance is prevalent.

Ma de Lourdes Garcia Garcia (Instituto Nacional de Salud Publica, Mexico) and colleagues analysed data from 436 tuberculosis patients from Southern Mexico treated with DOTS between 1995 and 2000. They found that the incidence of previously untreated, drugresistant cases fell by 84% from 9·4 to 1·5 per 100 000 people per year between 1996 and 2000. The incidence of patients presenting for retreatment dropped from 11·1 to 3·5 per 100 000 per year over the same period. The percentage of drug resistant tuberculosis also dropped. At the outset 22% of previously untreated patients with pulmonary TB were carrying drug-resistant strains, and 6·7% were MDR tuberculosis patients. In the final year of the study, only 7.8% of new patients were carrying drug resistant strains, and there were no new cases of MDR tuberculosis. However, patients with drug resistant tuberculosis, particularly MDR tuberculosis, had an increased likelihood of treatment failure and death. The authors conclude that additional interventions are needed to improve treatment outcomes.

Dr de Lourdes Garcia Garcia states: “DOTS can control both drug resistant and drug susceptible TB. Our prospective population based study shows that implementing DOTS in a health jurisdiction that had a moderate rate of drug resistant tuberculosis decreased the transmission of both drug susceptible and drug resistant tuberculosis. This was manifested by decreases in the tuberculosis incidence rate, the percentage of cases that were clustered, and the rate of newly diagnosed drug resistant cases.”

In an accompanying commentary Marcos Espinal (World Health Organization) concludes: “This study provides some reassurance that the introduction of DOTS will usually improve the standard of patient care and reduce transmission, rather than fanning the flames of an epidemic of multi-drug resistant tuberculosis. It also shows the need for the use of specific treatment for MDR-TB (DOTS-Plus) to prevent the high mortality rate among those carrying this type of tuberculosis.”