Multidrug-resistant tuberculosis strains 'more common than thought'
MedWire News: Multidrug-resistant (MDR) strains of tuberculosis are more common in China than previously assumed, study findings indicate.
"Addressing MDR tuberculosis in China will require selection of treatment regimens on the basis of testing for initial drug resistance. It is also important to improve treatment in tuberculosis hospitals and enhance the continuity of treatment after patients leave the hospitals," report Yu Wang (Chinese Center for Disease Control and Prevention, Beijing) and co-workers.
The team employed cluster-randomized sampling, with predetermined sample sizes across 70 clusters nationwide, to obtain a representative sample of patients with tuberculosis in China.
In all, 4606 patients took part in the study, and sociodemographic data on previous treatment for tuberculosis was gathered. In addition, two sputum samples were taken for each patient for tuberculosis and drug-susceptibility testing before the onset of treatment.
The findings, published in TheNew England Journal of Medicine, describe a sample of 3037 new cases of tuberculosis and 892 previously treated cases. Of these, 5.7% and 25.6%, respectively, were found to have MDR tuberculosis, which was defined as resistance to at least isoniazid and rifampin. This compared with 34.2% of new cases and 54.3% of previously treated cases that were resistant to at least one first-line antituberculosis drug.
In addition, it was shown that, among patients with MDR tuberculosis, 8.3% of new cases and 8.0% of previously treated cases had extensively drug-resistant tuberculosis (XDR), which was defined as resistance to at least isoniazid, rifampin, ofloxacin, and kanamycin. This corresponded to rates of 0.5% and 2.1% of the overall new and previous case samples.
In 2007, the team reports, there were 110,000 incidence cases of MDR tuberculosis and 8200 incident cases of XDR tuberculosis in China, the majority of which were due to primary transmission. The highest risk for MDR tuberculosis was seen in patients with multiple previous treatments who received their previous treatment in hospital, at an odds ratio of 13.3. It was estimated that 43.8% of patients did not complete their last treatment.
In an accompanying editorial, Richard Chaisson and Eric Nuermberger, from Johns Hopkins Medical Institutions in Baltimore, Maryland, discuss a range of ways in which MDR tuberculosis may be tackled, conceding that it represents an "enormous challenge."
By Liam Davenport