The World Health Organization (WHO) has ongoing programs to improve and monitor tuberculosis (TB). The WHO’s 2011 report on global TB control provides the most comprehensive information ever collected on the problems and issues of disease, as well as deaths caused by TB and multidrug-resistant TB (i.e. disease marked by in vitro resistance to at least isoniazid and rifampicin). They also look at treatment outcomes, financing mechanisms and new TB diagnostics, drugs and vaccines.
Known as The Global Project on Anti-tuberculosis Drug Resistance Surveillance, and launched in 1994, it has generated reliable drug resistance estimates for 127 countries based on representative studies that followed standard methods and separately looked at resistance among new and retreatment cases.
Published in the recent issue of the Bulletin, the article by Zignol et al., draws on those estimates to portray the best of current knowledge on anti-TB drug resistance, multidrug-resistant TB (MDR-TB) and extensively-drug-resistant TB (XDR-TB) (i.e. MDR-TB disease marked by additional in vitro resistance to at least one fluoroquinolone and one injectable drug).
The report gives public health and other institutions direction for future MDR-TB prevention and control. There are new molecular technologies, including line probe assays and Xpert® MTB/RIF, that can allow for the rapid diagnosis of thousands of MDR-TB cases, but unfortunately not all countries will be ready to treat those cases in compliance with appropriate guidelines.
This creates a certain amount of risk that new superstrains resistant to known treatments can develop, although there two forthcoming drugs : bedaquiline and delamanid that bolsters the arsenal of medications doctors can call on. The data presented by Zignol et al hastens implementation of these new approaches.
One area of focus is eastern Europe where, for example, a recent study found record rates of MDR-TB in Minsk, Belarus, where about half of all TB cases harbour MDR-TB strains. Many countries lack adequate monitoring or any at all, so urgent efforts need to be made to understand how MDR-TB is evolving in African countries, India and the Russian Federation.
et al’s report demonstrates that MDR-TB surveillance is improving and is a useful source of data for investigating the basic factors effecting MDR-TB. Sex did not emerge as an important determinant, and the long-feared association between MDR-TB and human immunodeficiency virus (HIV) infection was not supported by the study findings.
However, the unavailability of data on HIV serostatus for many countries … not surprising since only 34% of the world’s confirmed TB cases are tested for HIV, dictates caution in interpreting this finding. We are also reminded of how difficult it is to incorporate HIV testing in TB drug resistance surveys and of how far away we are from fully implementing the 12 activities for collaborative control of TB and HIV infection recommended by WHO.
One of the biggest problems is the mismanagement of non-drug resistant TB cases, and this issue remains prevalent even in high income European countries, where TB rarely occurs. There is a growing reservoir of difficult-to-treat cases, and this poses a real challenge to national TB programs and health providers the world over.
Written by Rupert Shepherd