The Pharmaceutical Journal
Vol 274 No 7344 p413
9 April 2005

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DOTS can reduce transmission and incidence of drug-resistant TB

A strategy that includes a short course of directly-observed therapy (DOTS) can rapidly reduce the transmission and incidence of both drug-susceptible and drug-resistant tuberculosis in settings with moderate rates of multidrug-resistant TB, according to research published this week.

Kathryn DeRiemer, Stanford University Medical Centre, California, and colleagues, conducted a study involving 436 patients in southern Mexico between 1995 and 2000. In 1996 changes were initiated in this area to bring it in line with the World Health Organization recommended DOTS strategy for TB control in Mexico.

The researchers screened people who reported coughing for longer than 15 days and identified patients with pulmonary TB. Retreatment cases were defined as patients who had previously received at least 30 days of anti-TB therapy.

Patients were followed up annually and three indicators of transmission were estimated for each 12-month period — the incidence rate of pulmonary TB, the percentage of pulmonary TB cases that were clustered and the rate of pulmonary TB with primary resistance to at least one first-line drug.

The results showed 323 cases of newly diagnosed TB, 109 retreatment cases and four patients whose previous treatment status was unknown.

The incidence rate of TB decreased by 54.4 per cent (P=0.00048) over five years. The percentage of cases that were clustered decreased by 62.6 per cent (P=0.02) and the size of the clusters also decreased. The number of new cases resistant to at least one first-line drug decreased by 84 per cent (P=0.004). By 2000, there were no new cases of multidrug-resistant TB and the rate of multidrug-resistant retreatment cases had decreased (P<0.0001).

However, the researchers highlight that although the rates of transmission and incidence of TB decreased significantly, the rates of treatment failure and mortality among patients with multidrug-resistant TB remained unacceptably high.

“Additional measures, such as drug-susceptibility testing and standard or individualised therapy, are needed to improve clinical outcomes,” the researchers say (Lancet 2005;365:1239).