Category II treatment is an eight-month regimen that adds injectable agent streptomycin to the standard four-drug regimen used to treat drug-sensitive TB. In 2010, the World Health Organization (WHO) began recommending drug-susceptibility testing for all previously treated TB patients. Drug-susceptibility testing (DST) is necessary for identifying drug-resistance and informing which drugs will work against an individual’s strain of TB. As countries scale-up rapid DST in line with WHO recommendations, category II treatment should be phased out. The replacement of category II treatment with DST-guided treatment stems from the fact that drug-resistance is more likely among patients that have been previously treated for TB, including those who have interrupted therapy or relapsed.
Category II treatment is still prescribed in India, even though there are already high rates of background resistance to streptomycin, and despite the fact that 2.2 percent of new TB cases and 15 percent of retreatment cases in India are drug-resistant. Adding a single drug to a first-line regimen that has failed to cure someone’s TB, as category II treatment does with streptomycin, is no longer in line with the global standard of care. Some studies suggest that category II treatment may be more likely to foster the development of further resistance than to cure TB. This may explain why India only achieves a treatment success rate of 66 percent among previously treated TB patients compared to 88 percent among new cases.
The Government of India urgently needs to replace category II treatment with DST-guided therapy for all previously treated TB patients. Cartridge-based nucleic acid amplification tests (CB-NAATs), like GeneXpert MTB/RIF, allow for the rapid detection of TB and resistance to rifampin—a key component of the regimen used to treat drug-sensitive TB—and signal the need for further DST alongside initiation of treatment with second-line TB drugs to which the patient’s strain of TB is more likely to be susceptible.