Totally drug-resistant TB may just be a misnomer

The reportedly developing "totally drug-resistant" tuberculosis in India may be an advanced stage of drug-resistant TB, which scientists called totally drug-resistant for lack of a better term.

Zarir Udwadia, a doctor from PD Hinduja National Hospital and Medical Research Center in Mumbai, reported on several cases of what is called TDR-TB in four patients who had no response to 12 TB drugs. Drug-resistant TB develops when patients take substandard drugs or do not complete six months of antibiotics treatment, IRIN reports.

The World Health Organization explained in a briefing note on January 13 that the lack of international standards on lab testing make it difficult to determine if a strain of TB is incurable. There were six TB drugs in the WHO treatment guidelines that were not tested by the Indian labs. In addition, while a strain of TB may not respond to a drug in a lab, it may respond in an infected person. TDR-TB cases may involve an extensively drug-resistant TB strain that has not been properly tested.

New anti-TB drugs are also under development and their effectiveness against the reportedly TDR-TB can not yet be proven. In March, the WHO will convene a meeting of TB experts to consider whether or not a new TB definition is required.

"If 'totally drug-resistant' TB defines a subset of XDR-TB with different characteristics to other XDR-TB cases, particularly with respect to the outcome of such cases, then an internationally recognized definition may be needed," the WHO said, according to IRIN.

There have been 21 cases labeled TDR-TB in India, Iran, Italy and Germany. At the conclusion of 2010, 69 countries reported at least one case of XDR-TB to the WHO.