Use of Standard TB Treatments To Treat MDR-TB Ineffective, Could Lead to Increased Drug Resistance in Countries With High MDR-TB Prevalence, Study Says

The use of standard tuberculosis treatment methods to treat people with multi-drug resistant TB is ineffective in countries with high rates of MDR-TB and could lead to increased drug resistance, according to a study published in the Aug. 1 issue of the American Journal of Respiratory and Critical Care Medicine, Reuters Health reports (Reuters Health, 8/1).

For the study, Dick Menzies, director of the Respiratory Division at McGill University in Montreal, and colleagues reviewed World Health Organization data from 2003 and 2004 and examined the association between drug resistance and treatment outcomes in 155 countries. Of the 155 countries, 121 reported at least 250 MDR-TB annually (ANI/Yahoo! India News, 8/2). The cases were treated with standard TB regimens (Reuters Health, 8/1). The researchers reviewed nonadherence, treatment failure, relapse and death rates following initial treatment and retreatment. They then analyzed the rates with respect to MDR-TB prevalence in each country.

The study found that treatment failure rates were significantly higher in countries with a high prevalence of MDR-TB. After accounting for age, HIV prevalence, per capita income and treatment regimen, the researchers calculated that every 1% increase in MDR-TB prevalence was associated with a 0.3% increase in treatment failure among new cases, a 1.1% increase in failure among retreatment cases, and a 1% increase in relapse. In addition, the study found that 21.4% of TB patients required retreatment in countries with an initial MDR-TB prevalence of greater than 3%, compared with 11.9% of patients who required retreatment in countries with an initial MDR-TB prevalence of less than 1% (ANI/Yahoo! India News, 8/2). Furthermore, retreatment outcomes were generally poor in all countries, with high rates of relapse, failure and death, the study found.

According to the researchers, it is "urgent" that countries with an initial MDR-TB prevalence of greater than 3% "strengthen capacity to perform drug sensitivity testing" or "re-examine" standard TB treatment regimens (Reuters Health, 8/1). Menzies said the study provides "striking evidence that MDR-TB is directly linked to the increased failure rates of our current treatment regimens." In the short term, the "higher failure and relapse rates mean greater morbidity and mortality for patients with greater social and economic" implications in countries with a high MDR-TB prevalence, Menzies said, adding that the use of standard TB regimens to treat MDR-TB could lead to an increased number of MDR-TB cases in the long term (ANI/Yahoo! India News, 8/2).

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Existing MDR-TB control methods are "decades old, complex to use, time consuming and, more importantly, not designed for case management" of MDR-TB, Marcos Espinal, executive director of the Stop TB Partnership, and Mario Raviglione, director of WHO's Stop TB Department, write in an accompanying editorial. They add that "[u]nless 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 decades to come" (Reuters Health, 8/1).

An abstract of the study is available online.