Even as the Union health ministry has sent a team of doctors to Mumbai to ascertain facts about the reported cases of drug resistant tuberculosis cases, the ministry has taken strong exception to the term ‘totally drug resistant’ TB, which, the ministry said, is non-standardized and misleading.
“The term ‘totally drug resistant’ TB is non-standardized and is misleading; testing for resistance beyond XDR-TB is not advocated by WHO and poor clinical response to treatment has not yet been correlated with diagnosis of drug resistant TB without laboratory conformation from accredited labs,” a ministry release said.
Multi-Drug Resistant (MDR-TB) is defined as resistance to at least isoniazid and rifampicin (two of the most potent first line anti-TB drugs), with or without resistance to other first-line drugs; extensively drug-resistant TB (XDR-TB) is defined as resistance to at least rifampicin, isoniazid (i.e. MDR-TB) plus resistance to any fluoroquinolone, and to any of the 3 second-line injectable drugs (capreomycin, kanamycin and amikacin), the ministry release said.
Perturbed over the repeated use of the word ‘totally drug resistant’ TB by the medical fraternity, the ministry further said that the term “totally drug resistant” tuberculosis is neither recognized by the WHO nor by Revised National Tuberculosis Control Programme (RNTCP). For now these cases are defined as extensively drug resistant tuberculosis (XDR-TB), according to WHO definitions, and accordingly can be managed by national XDR-TB treatment guidelines. Current WHO recommendations advise against the use of the drug susceptibility testing (DST) results for second line drugs beyond those used to identify XDR-TB to guide treatment.
Any type of drug resistant TB can only be diagnosed by laboratory test and not by clinical examination alone. Preliminary results of second-line DST for MDR-TB patients from DOTS plus sites and also isolates collected from Gujarat and Maharashtra drug resistance surveys show that there is not yet any XDR-TB amongst new cases and 0.5 per cent amongst re-treatment cases.