Reversing the tide of tuberculosis in India: complementing microscopy with line probe assays

In 1993, the World Health Organisation (WHO) declared tuberculosis (TB) a global health threat, adopted the Directly Observed Therapy - Short Course (DOTS) strategy, and set two targets for control and elimination of the disease: to detect 70% of sputum smear positive cases and to successfully treat 85% of those cases. The recommended diagnostic tool under DOTS remains sputum smear microscopy, a simple, yet ineffective, technique that only detects roughly half of TB cases. In India, where TB killed 450,000 people in 2005, both WHO targets for detection and treatment were met in the smear positive population covered by DOTS. However, HIV co-infection and multidrug-resistant TB (MDR-TB) pose formidable threats to TB control: TB in HIV-positive patients is often smear-negative, and microscopy cannot detect drug resistance. Although, the reliance on DOTS has proven effective in areas where both HIV prevalence and drug resistance are low, in India, the National TB Programme should consider complementing the antiquated technique of microscopy in order to diagnose smear-negative, extrapulmonary, and MDR-TB cases. Integrating existing rapid molecular diagnostics with the Indian National TB Programme is timely, and would be extremely beneficial to address the two major threats to TB control in the country.