Tuberculosis — Diagnosis & DOTS Treatment
Tuberculosis is diagnosed in 26 lakh Indians every year and kills 4 lakh annually. India is the world's highest TB burden country. The NTEP provides free diagnosis (CBNAAT, Truenat, sputum microscopy) and treatment (daily regimen, MDR regimen) for every TB patient. For MBBS doctors in India, TB knowledge is non-optional — every doctor will encounter TB patients throughout their career.
Tuberculosis is caused by Mycobacterium tuberculosis, an acid-fast bacillus transmitted via respiratory droplet nuclei. After infection, 5-10% develop active TB in their lifetime (highest risk in first 2 years). Risk factors: HIV, diabetes, malnutrition, smoking, immunosuppression, chronic kidney disease, silicosis, anti-TNF therapy. Pulmonary TB is most common (85%); extra-pulmonary TB affects lymph nodes, pleura, bones, meninges, pericardium, intestine.
Pulmonary TB:
- Symptoms: Cough > 2 weeks, sputum production, haemoptysis, fever (especially evening), night sweats, weight loss, anorexia, chest pain
- Sputum smear microscopy (ZN stain): Two samples (on-the-spot and early morning). Sensitivity 50-60% — misses paucibacillary TB
- CBNAAT (Xpert MTB/RIF): Molecular test detects M. tuberculosis DNA + rifampicin resistance in 2 hours. Sensitivity > 90% for smear-positive, 70-80% for smear-negative. First-line test for: paediatric TB, HIV-TB, extra-pulmonary TB, previously-treated TB
- Truenat: Chip-based molecular test at PHC level — same-day rifampicin resistance
- LPA (Line Probe Assay): For first-line (FL-LPA) and second-line (SL-LPA) drug resistance
- Chest X-ray: Apical/posterior upper lobe infiltrates, cavitation, pleural effusion, miliary pattern
Extra-pulmonary TB:
- TB lymphadenitis: FNAC — caseating granuloma; CBNAAT on tissue
- TB pleural effusion: Pleural fluid — lymphocytic exudate, ADA > 40 U/L; CBNAAT on fluid (low sensitivity)
- TB meningitis: CSF — lymphocytic pleocytosis, high protein, low glucose; CBNAAT on CSF
- Bone/joint TB: X-ray (vertebral collapse — Pott's spine), MRI; biopsy with CBNAAT
- Abdominal TB: Colonoscopy with biopsy; CBNAAT on tissue
| Drug | Daily Dose (mg/kg) | Key Side Effects |
|---|---|---|
| Rifampicin (R) | 10 (max 600) | Orange urine, hepatotoxicity, GI upset, drug interactions (OCP, warfarin, antiretrovirals) |
| Isoniazid (H) | 5 (max 300) | Hepatotoxicity, peripheral neuropathy (give pyridoxine 10 mg OD), psychosis |
| Pyrazinamide (Z) | 25 (max 2 g) | Hepatotoxicity, hyperuricaemia, arthralgia |
| Ethambutol (E) | 15 (max 1.6 g) | Optic neuritis (red-green colour blindness, blurring), require baseline and monthly vision check |
| Streptomycin (S, second-line) | 15 IM | Ototoxicity, nephrotoxicity |
| MDR-TB drugs: | Levofloxacin, Moxifloxacin, Bedaquiline, Delamanid, Linezolid, Clofazimine, Cycloserine, Para-aminosalicylic acid, Amikacin, Capreomycin | Various — QT prolongation (Bedaquiline, Delamanid), myelosuppression (Linezolid), psychiatric (Cycloserine) |
Drug-sensitive pulmonary TB (new adult): 6 months total
- Intensive phase (2 months): HRZE daily — weight-band FDC tablets
- Continuation phase (4 months): HR daily
- Total: 6 months (2HRZE + 4HR)
TB meningitis / bone & joint TB: 12 months (2HRZE + 10HR). Add corticosteroids for TB meningitis (dexamethasone taper over 6-8 weeks) — reduces mortality.
Previously treated TB (relapse, treatment failure, default): 8 months (2HRZES + 1HRZE + 5HRE). Always send for drug susceptibility testing before starting re-treatment.
Childhood TB: Same drug-sensitive regimen. Ethambutol omitted in children < 5 years (cannot report visual symptoms).
TB Preventive Treatment (TPT): For contacts of confirmed TB cases, especially children < 5 years and PLHIV. Regimens: 6H (Isoniazid 6 months — older), 3HP (Rifapentine + Isoniazid weekly x 3 months — newer), 4R (Rifampicin daily x 4 months).
MDR-TB: Resistance to at least Rifampicin and Isoniazid. Treatment: shorter 9-month all-oral regimen (4-6 Bdq[6m]-Lfx-Cfz-Z-E-Hh-Eto/ 5 Lfx-Cfz-Z-E) OR longer 18-20 month individualised regimen.
Pre-XDR-TB: MDR + resistance to any fluoroquinolone (Levofloxacin or Moxifloxacin).
XDR-TB: MDR + resistance to any fluoroquinolone + at least one additional Group A drug (Bedaquiline or Linezolid).
BPaLM regimen (6 months all-oral, 2022 onwards): Bedaquiline + Pretomanid + Linezolid ± Moxifloxacin. For pre-XDR-TB and treatment-intolerant or non-responsive MDR-TB. Linezolid dose 600 mg — may reduce to 300 mg or stop if myelosuppression, neuropathy.
TB is the disease every Indian doctor must know cold — from diagnosis (CBNAAT indications) to treatment (daily DOTS regimen) to MDR-TB (BPaLM). For UPSC CMS aspirants, TB is among the most predictable PSM and clinical interview topics.