A 35-year-old man from rural India presents with a 3-month history of cough, fever, and weight loss. Chest X-ray shows cavitary lesions in the right upper lobe. Sputum smear microscopy is positive for acid-fast bacilli. He is started on standard anti-tuberculous therapy. Which is the most common cause of treatment failure in tuberculosis in India?

## Most Common Cause of TB Treatment Failure **Key Point:** Poor drug adherence and irregular treatment is the single most common cause of treatment failure in tuberculosis, accounting for >80% of failures in resource-limited settings like India. ### Why Adherence Matters Tuberculosis treatment requires a minimum of 6 months of continuous therapy with multiple drugs. Even brief interruptions allow: - Mycobacterial regrowth - Selection of resistant strains - Relapse and treatment failure ### Epidemiology in India | Cause of TB Treatment Failure | Frequency | Comment | | --- | --- | --- | | Poor adherence / irregular treatment | 80–85% | Most common; preventable | | MDR-TB (primary resistance) | 5–10% | Increasing but less common initially | | Malabsorption | 2–5% | Rare; seen in GI disease or HIV | | Concurrent HIV | 3–8% | Important but not the commonest cause | **Clinical Pearl:** DOTS (Directly Observed Therapy, Short course) was specifically designed to address adherence issues by having a health worker observe each dose. This remains the cornerstone of TB control in India. **High-Yield:** In the NEET PG exam, when asked about the most common cause of TB treatment failure, the answer is almost always **poor adherence** unless the stem explicitly mentions drug resistance or immunosuppression. **Tip:** Do not confuse "most common cause of treatment failure" with "most common cause of treatment-resistant TB." MDR-TB is a microbiological resistance issue; poor adherence is a programmatic issue and is far more frequent.