Step‑by‑Step Diagnosis and First‑Line Treatment of Tuberculosis in India

1. Clinical Suspicion and History

Patients presenting with chronic cough (>3 weeks), haemoptysis, weight loss, night sweats or low‑grade fever should be evaluated for TB. In India, a high index of suspicion is essential due to the disease’s endemicity and the presence of comorbidities such as diabetes or HIV.

2. Initial Screening

• Mantoux Test (PPD): 0.1 mL of purified protein derivative injected intradermally; induration ≥10 mm in HIV‑negative, 5 mm in HIV‑positive or immunocompromised patients is considered positive.
• TB GeneXpert MTB/RIF: Rapid molecular assay performed on a single sputum sample; detects Mycobacterium tuberculosis DNA and rifampicin resistance within 2 hours.

3. Sputum Collection and Microscopy

1. Sample Timing: Early morning sputum is preferred due to higher bacillary load.
2. Number of Samples: Collect at least three specimens on consecutive days (Day 1, Day 2, Day 3).
3. Anaerobic Transport: Use sterile containers; if delayed >4 hours, refrigerate at 4°C.
4. Ziehl‑Neelsen Stain: Acid‑fast bacilli (AFB) detected under oil immersion. AFB count ≥10 per 100 fields indicates smear‑positive TB.
5. Liquid Culture (MGIT 960): Increases sensitivity; results available in 7–14 days.

4. Radiological Evaluation

1. Chest X‑Ray (PA and Lateral): Look for upper lobe infiltrates, cavitation, pleural effusion. In India, portable digital X‑ray units are widely available in district hospitals.
2. CT Scan: Reserved for cases with complicated disease (mediastinal lymphadenopathy, suspected extrapulmonary TB).
3. High‑Resolution CT (HRCT): Useful for diagnosing chronic cavitary lesions or post‑treatment sequelae.

5. Additional Laboratory Tests

• Sputum GeneXpert MTB/RIF Ultra: Detects rifampicin resistance; crucial for MDR‑TB screening.
• HIV Serology: All TB patients should be screened for HIV; CD4 count and viral load guide treatment.
• Baseline Hematology: CBC, ESR to monitor for drug toxicity.
• Liver Function Tests: ALT, AST baseline; monitor every 2 weeks during treatment.
• Renal Function: Serum creatinine baseline; adjust dosages if eGFR <30 mL/min.

6. Diagnosis Confirmation

A diagnosis of pulmonary TB is confirmed if at least one of the following is positive:

• Positive sputum AFB smear.
• Positive GeneXpert MTB/RIF.
• Culture positivity for M. tuberculosis.

7. First‑Line Anti‑Tubercular Therapy (ATT) – 6‑Month Regimen

India follows the Revised National Tuberculosis Control Programme (RNTCP) regimen:

All doses are adjusted for weight; children receive weight‑based dosing. The regimen is administered directly observed therapy (DOT) to ensure adherence.

8. Monitoring and Managing Drug Toxicity

• Liver Enzymes: AST/ALT >5× ULN warrants temporary discontinuation.
• Visual Acuity: Ethambutol causes optic neuropathy; assess at baseline, 2 weeks, and monthly.
• Hematology: Isoniazid can cause thrombocytopenia; monitor CBC every 4 weeks.
• Adherence Support: Use mobile health reminders, community DOT personnel.

9. Special Situations in India

• MDR‑TB (Rifampicin & Isoniazid Resistant): Switch to second‑line regimen – levofloxacin 750 mg, kanamycin 1 g, ethionamide 1500 mg, cycloserine 500 mg.
• HIV‑Positive Patients: Initiate antiretroviral therapy (ART) within 2 weeks of starting ATT; monitor drug–drug interactions.
• Pregnancy: Isoniazid and rifampicin are category B; pyrazinamide is also acceptable. Ethambutol is avoided in the first trimester due to ocular toxicity.

10. Follow‑Up and Treatment Completion

After 6 months, repeat sputum smear or GeneXpert. A negative result confirms cure. Record treatment outcomes in the National TB Programme database for surveillance.

11. Summary of Key Points

• Early sputum collection and GeneXpert testing are critical for rapid diagnosis.
• Standard 6‑month regimen remains effective; DOT ensures adherence.
• Regular monitoring for hepatotoxicity and visual changes is mandatory.
• MDR‑TB and HIV co‑infection require modified regimens and close coordination.

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