NEW YORK (Reuters Health) - In certain “hot zones” where multidrug-resistant tuberculosis is prevalent, patients treated with standard TB drugs have high rates of failure and relapse, new research indicates.

An inmate sits in the multi-drug resistant tuberculosis (MDR-TB) ward in a prison hospital in the Siberian city of Tomsk, east of Moscow, June 4, 2008. REUTERS/Thomas Peter

In countries where “drug sensitivity testing” is not performed routinely, the current standard anti-TB drug regimens “may be contributing to worsening drug resistance levels,” a multinational research team warns in a report published Friday.

Dr. Dick Menzies, from McGill University in Montreal, and colleagues analyzed the association between drug resistance and treatment outcome in 103 countries, which were selected because their multidrug-resistant TB prevalences were known and because they had each reported on outcomes for more than 250 cases treated with standard treatment regimens in 2003 and/or 2004.

The researchers calculated that every 1 percent increase in the initial prevalence of multidrug-resistant TB was associated with a 0.3 percent increase in treatment failure among new cases, a 1.1 percent increase in failure among retreatment cases, and a 1 percent increase in relapse. The results are statistically significant, the researchers note.

Menzies and his team believe that in countries where initial multidrug-resistant TB prevalence is at least 3 percent, “it is urgent to strengthen capacity to perform drug sensitivity testing, or to reexamine standardized (initial treatment and retreatment) regimens.”

In these countries, more than 20 percent of treated patients required retreatment, their report indicates. Moreover, in all countries, retreatment outcomes were generally poor, with high rates of default, failure, and death.

The investigators warn, “Failure to act now will mean far more resources will be needed in the long run to address global drug resistance.”

Drs. Marcos Espinal and Mario C. Raviglione, with the World Health Organization in Geneva, Switzerland, agree, noting in an editorial that current tools for managing multidrug-resistant TB “are decades old, complex to use, time consuming, and more importantly, not designed for case management of multidrug-resistant TB.”

“Unless those with the responsibility to boost control and research efforts increase their commitments and their financial investments by several fold, we may never see elimination of this major scourge in the decades to come,” the editorial concludes.

SOURCE: American Journal of Respiratory and Critical Care Medicine, August 1, 2008.