Tuberculosis Diagnosis & Treatment for NEET PG — Complete Guide 2026

Version 1.0 — Published April 2026

Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis complex — and in India, it is the highest-yield infectious disease topic for NEET PG. The student who masters ATT regimens, drug side effects (HIEP), and MDR-TB treatment has covered the foundation for 3–5 marks across medicine, pharmacology, and microbiology papers. Pair this guide with daily MCQ practice on the Medicine subject hub, cross-reference the high-yield medicine topics overview, and revise high-yield microbiology topics for the organism-level detail.

Epidemiology — India's burden and NTEP

India accounts for approximately 27% of the global TB burden — the highest of any country — with an estimated 2.8 million incident TB cases per year and 320,000 TB deaths annually (WHO Global TB Report 2024).

Key epidemiology numbers:

• Incidence: ~199 cases per 100,000 population per year
• HIV co-infection: ~3% of TB cases in India
• Treatment success rate: 85% for new drug-sensitive TB (NTEP 2023)
• MDR-TB burden: ~135,000 cases per year (~5% of total)
• RR-TB detection rate: ~65% of estimated MDR cases

NTEP (National Tuberculosis Elimination Programme):

• Renamed from RNTCP (Revised National TB Control Programme) in 2020
• Operates via 5-tier structure: Central TU → State TU → District TU → TB Unit → DMC (Designated Microscopy Centre) / PHI
• Universal DST (drug sensitivity testing) at baseline since 2018
• Daily regimen since 2017 (replaced the old thrice-weekly intermittent DOTS)
• TB elimination target: 2025 (India) vs 2030 (global SDG)

Nikshay Poshan Yojana: ₹500/month direct benefit transfer to every notified TB patient for nutritional support — a flagship NTEP intervention.

Pathogenesis — primary vs post-primary TB

TB pathogenesis is a cell-mediated immune response to Mycobacterium tuberculosis, with two distinct clinical-pathological forms.

Primary TB (first exposure, usually childhood):

1. Inhaled droplet nuclei reach alveoli
2. Alveolar macrophages phagocytose bacilli; replication inside phagosome
3. Subpleural granuloma forms in middle zone (lower part of upper lobe or upper part of lower lobe) — the Ghon focus
4. Bacilli drain to hilar lymph nodes — Ghon complex = Ghon focus + hilar lymphadenitis
5. When calcified → Ranke complex
6. Cell-mediated immunity (Th1, IFN-gamma, macrophage activation) controls infection in 90%
7. 10% progress to primary progressive TB or disseminate (miliary, TBM)
8. Simon focus: apical nodule seeded during primary infection — future reactivation site

Post-primary (reactivation / secondary) TB (adults):

• Occurs in apical posterior segments of upper lobes and superior segment of lower lobes
• Reason: high oxygen tension favours Mycobacterium growth
• Caseation necrosis liquefies and drains via bronchus → cavity + bronchogenic spread
• Reactivation triggers: HIV, diabetes, malnutrition, steroids, anti-TNF agents, silicosis, CKD

Histology hallmark: Caseating granuloma with Langhans giant cells, epithelioid histiocytes, lymphocytic cuff, central caseous necrosis. Acid-fast bacilli on Ziehl-Neelsen stain (red-pink rods on blue background).

Clinical presentation — pulmonary and extrapulmonary

Pulmonary TB accounts for 75–80% of cases in adults; extrapulmonary TB (EPTB) accounts for 20–25%, rising to 40–50% in HIV co-infection.

Pulmonary TB symptoms (classic tetrad):

1. Chronic cough >2 weeks (NTEP screening criterion)
2. Evening-rise (low-grade) fever with night sweats
3. Weight loss, anorexia
4. Hemoptysis (cavitary disease)

EPTB by site (high-yield):

Diagnosis — CBNAAT, culture, and the rest

TB diagnosis is a stepwise algorithm, and under NTEP Universal DST policy, CBNAAT is the preferred initial test for every presumptive TB case.

Sputum smear (Ziehl-Neelsen):

• 2 samples (spot + early morning, or 2 spot 1 hour apart)
• Sensitivity 60–70%; requires 10,000 bacilli/mL
• LED fluorescence microscopy (auramine-rhodamine) increases yield

CBNAAT / Xpert MTB/RIF:

• Cartridge-based PCR on GeneXpert platform
• Detects M. tuberculosis DNA + rifampicin resistance (rpoB gene)
• Result in ~2 hours
• Sensitivity 88% (smear-positive 98%, smear-negative 68%)
• Xpert MTB/RIF Ultra has higher sensitivity (especially paucibacillary samples) but more "trace" results

Culture (gold standard):

• Solid: Lowenstein-Jensen medium — 6–8 weeks to grow
• Liquid: MGIT 960 (Mycobacterial Growth Indicator Tube) — 10–14 days
• Required for phenotypic DST to second-line drugs

Line Probe Assay (LPA):

• First-line LPA: detects INH + RIF resistance (katG, inhA, rpoB genes)
• Second-line LPA: detects fluoroquinolone + aminoglycoside resistance
• Done on smear-positive sputum or culture isolate

Mantoux (tuberculin skin test):

• 5 TU PPD intradermal (left forearm), read induration at 48–72 hours
• Positive cutoffs:
  • >=5 mm: HIV, immunocompromised, recent close contacts, fibrotic CXR
  • >=10 mm: Healthcare workers, high-prevalence populations, children <4 years, IV drug users, chronic illness
  • >=15 mm: Low-risk adults
• BCG causes false positive up to 15 mm; wanes after 10 years
• False negatives: active severe TB, HIV, malnutrition, immunosuppressants, recent live vaccine

IGRA (QuantiFERON-TB Gold, T-SPOT.TB):

• Whole-blood assay measuring IFN-gamma release to ESAT-6 and CFP-10 antigens (absent in BCG)
• No BCG false positive; single visit
• Cannot distinguish latent from active TB

Adenosine deaminase (ADA):

• Pleural: >40 U/L supports TB pleural effusion
• CSF: >10 U/L supports TBM
• Ascitic fluid: >39 U/L supports peritoneal TB

Chest X-ray patterns

Chest X-ray is the first imaging modality in pulmonary TB and shows pattern-specific findings that map to disease stage.

HIV-TB radiographic atypia: Early HIV (CD4 >300) looks like typical reactivation TB. Advanced HIV (CD4 <200) shows lower lobe infiltrates, minimal cavitation, mediastinal adenopathy, and up to 15% have normal chest X-ray despite active pulmonary TB.

NTEP treatment regimens

NTEP treatment is weight-band-based daily fixed-dose combinations (FDCs), administered under supervision or via 99DOTS / MERM adherence monitoring.

Regimens (2021 update — daily, weight-banded):

H = isoniazid (5 mg/kg), R = rifampicin (10 mg/kg), Z = pyrazinamide (25 mg/kg), E = ethambutol (15 mg/kg) in daily regimen.

Key NTEP policy changes (post-2018):

• Universal DST at baseline — CBNAAT done on every presumptive TB case
• Old Category II (8-month SHRZE) phased out — any previously-treated case now gets DST-guided therapy
• Daily regimen replaced thrice-weekly DOTS in 2017 (2H3R3Z3E3 no longer used)
• Pediatric FDCs with dispersible tablets since 2019
• Nikshay Poshan Yojana ₹500/month nutritional DBT
• Active case finding among vulnerable populations (migrant workers, urban slums, tribal areas)

EPTB duration:

• Lymph node, pleural, abdominal: 6 months (2HRZE + 4HRE)
• CNS TB (TBM, tuberculoma): 12 months (2HRZE + 10HRE) + adjunctive dexamethasone
• Bone / joint TB (Pott's): 9–12 months
• Disseminated / miliary: 6–9 months

Adjunctive steroids (dexamethasone or prednisolone) indicated in:

• TB meningitis (proven RCT mortality benefit)
• TB pericarditis
• Severe pleural / peritoneal TB
• Large tuberculoma with mass effect
• Adrenal TB

ATT side effects — the HIEP approach

ATT side effects are predictable, detectable, and the HIEP mnemonic maps each drug to its signature toxicity.

Drug-induced hepatitis protocol (DIH):

• Symptomatic hepatitis OR ALT >=3× ULN with symptoms OR ALT >=5× ULN without symptoms → stop all hepatotoxic drugs (H, R, Z)
• Continue E + add levofloxacin + streptomycin
• Once LFT normalises, reintroduce drugs one at a time at 3-day intervals (R first, then H, then Z)
• Identify the culprit, substitute long-term

Pregnancy and ATT:

• H, R, E, Z are all considered safe in pregnancy (WHO 2021)
• Streptomycin is teratogenic (VIIIth nerve damage) — avoid
• Pyridoxine 25 mg daily + breastfeeding can continue on ATT

Pediatric weight-banded dosing: H 10 mg/kg, R 15 mg/kg, Z 35 mg/kg, E 20 mg/kg.

MDR-TB and XDR-TB

Drug-resistant TB is a growing public health crisis, and the WHO 2021 definition changes are a common exam update.

Definitions (WHO 2021):

• Mono-resistant: resistance to one first-line drug (excluding MDR)
• Poly-resistant: resistance to >1 first-line drug, excluding MDR
• MDR-TB: resistance to at least isoniazid + rifampicin
• Rifampicin-resistant (RR-TB): any rifampicin resistance (treated like MDR)
• Pre-XDR-TB: MDR-TB + fluoroquinolone resistance
• XDR-TB (2021 revised): MDR-TB + fluoroquinolone resistance + resistance to at least one Group A drug (bedaquiline or linezolid)

WHO drug groups (2020) for MDR-TB design:

Current preferred regimens (NTEP 2022+):

• BPaL (6 months): bedaquiline + pretomanid + linezolid — for pulmonary pre-XDR / XDR-TB (ZeNix trial)
• BPaLM (6 months): BPaL + moxifloxacin — for fluoroquinolone-sensitive MDR/RR-TB (TB-PRACTECAL trial)
• Shorter all-oral regimen (9–11 months) for selected MDR/RR-TB without FQ resistance
• Longer individualised regimen (18–20 months) if above not suitable

Key drug-specific points:

• Bedaquiline: QTc prolongation — baseline and monthly ECG; avoid with other QT-prolonging drugs
• Linezolid: peripheral neuropathy, optic neuropathy, myelosuppression; monitor CBC and vision
• Clofazimine: skin discolouration (reddish-brown), QTc prolongation
• Pretomanid: hepatitis; approved only as part of BPaL/BPaLM

Latent TB infection

Latent TB infection (LTBI) is the presence of M. tuberculosis immune sensitisation without clinical or radiographic active disease — and treating LTBI prevents future reactivation in 60–90% of patients.

Diagnosis of LTBI (all 3 required):

1. Positive Mantoux or IGRA
2. No symptoms of active TB
3. Normal chest X-ray (or only fibrotic lesions without activity)

Who to screen for LTBI (NTEP 2021):

• Household contacts of smear-positive / CBNAAT-positive TB cases
• All HIV-positive individuals
• Patients starting anti-TNF biologics or other immunosuppressants
• Pre-transplant recipients
• Silicosis, CKD on dialysis
• Healthcare workers in high-burden settings

Treatment regimens:

BCG vaccination (India):

• Single dose at birth (along with OPV-0, Hepatitis B birth dose)
• Live attenuated Mycobacterium bovis
• Protects against disseminated TB and TBM in children (~80% efficacy)
• Poor protection against adult pulmonary TB
• Contraindicated in symptomatic HIV and severe immunodeficiency

Sources and references

1. World Health Organization — Global Tuberculosis Report 2024 — authoritative source for incidence, mortality, and MDR burden by country.
2. Central TB Division, Ministry of Health & Family Welfare, Government of India — NTEP Technical and Operational Guidelines for TB Control (2021 edition) and 2022 updates for MDR/XDR regimens.
3. Harrison's Principles of Internal Medicine, 21st Edition (Loscalzo et al., 2022) — Chapter on Tuberculosis.
4. WHO Consolidated Guidelines on Tuberculosis — Module 4: Treatment (2022 update) — BPaL, BPaLM regimen evidence.
5. Nahid P et al. Treatment of Drug-Susceptible Tuberculosis: ATS/CDC/IDSA Clinical Practice Guidelines. Clinical Infectious Diseases 2016; 63:e147-e195.
6. API Textbook of Medicine, 11th Edition (Munjal et al., 2019) — Indian clinical perspective on TB.

Frequently asked questions

How many TB questions appear in NEET PG?

Tuberculosis contributes 3-5 direct questions per NEET PG paper across medicine, pharmacology, microbiology, and community medicine. ATT regimen by category, drug side effects (HIEP mnemonic), CBNAAT interpretation, and MDR-TB treatment are the most tested subtopics based on 2019-2025 pattern analysis.

What is India's TB burden?

India accounts for approximately 27 percent of the global TB burden — the highest of any country — with an estimated 2.8 million incident cases per year (WHO Global TB Report 2024). The government has adopted a National Strategic Plan target of TB elimination by 2025, five years ahead of the global SDG target of 2030. NTEP (formerly RNTCP) is the delivery vehicle.

What is the difference between primary and post-primary TB?

Primary TB occurs on first exposure, usually in children, and features the Ghon focus (subpleural granuloma in lower part of upper lobe or upper part of lower lobe) plus hilar lymphadenopathy — together the Ghon complex (Ranke complex when calcified). Post-primary (reactivation) TB occurs in adults, typically in apical posterior segments of upper lobes due to high oxygen tension, and cavitates.

What is CBNAAT and when is it preferred over sputum smear?

CBNAAT (Cartridge-Based Nucleic Acid Amplification Test) uses the Xpert MTB/RIF platform to detect Mycobacterium tuberculosis DNA and rifampicin resistance in 2 hours. It has higher sensitivity than smear (88 percent vs 60 percent) and detects rifampicin resistance directly. Under NTEP, CBNAAT is now the preferred initial diagnostic test for all presumptive TB cases (Universal DST policy).

What are the NTEP categories and ATT regimens?

Under NTEP (daily regimen, 2021 update), there are two categories. New cases receive 2 months of HRZE intensive phase plus 4 months of HRE continuation phase (2HRZE + 4HRE). Previously treated cases (relapse, failure, loss to follow-up) now receive the same regimen with universal drug sensitivity testing at baseline — the old Category II (SHRZE 8-month regimen) has been phased out.

What are the side effects of first-line ATT (HIEP mnemonic)?

The HIEP mnemonic captures first-line ATT toxicity. H (isoniazid): hepatitis, peripheral neuropathy — prevented by pyridoxine 10 mg daily. R (rifampicin): hepatitis, red-orange body fluids, flu-like syndrome, enzyme induction. Z (pyrazinamide): hepatitis, hyperuricemia with gout, arthralgia. E (ethambutol): retrobulbar optic neuritis — dose 15 mg/kg in daily regimen to minimize.

How do you diagnose TB meningitis?

TB meningitis diagnosis requires a high index of suspicion. CSF shows elevated protein (often greater than 100 mg/dL), low glucose (less than 40 mg/dL or CSF/serum ratio less than 0.5), lymphocytic pleocytosis (100-500 cells), and sometimes a cobweb clot. CBNAAT on CSF is the preferred confirmatory test (sensitivity 70-80 percent). Treatment is 12 months of ATT with adjunctive dexamethasone.

What defines MDR-TB and XDR-TB?

MDR-TB is resistance to at least isoniazid AND rifampicin. Pre-XDR-TB is MDR-TB plus resistance to any fluoroquinolone. XDR-TB (WHO 2021 revised definition) is MDR-TB plus resistance to any fluoroquinolone AND at least one additional Group A drug (bedaquiline or linezolid). MDR-TB treatment now uses all-oral shorter regimens — 6-month BPaL (bedaquiline, pretomanid, linezolid) or BPaLM (+ moxifloxacin).

How is latent TB treated?

Latent TB infection (positive Mantoux or IGRA with no clinical or radiological evidence of active TB) is treated to prevent reactivation. Preferred regimen under NTEP is 3HP (isoniazid 900 mg plus rifapentine 900 mg weekly for 12 doses, given under supervision). Alternative regimens include 6-9 months of daily isoniazid or 3-4 months of daily rifampicin. Screen all household contacts of TB patients and HIV-positive individuals.

What is the Mantoux test cutoff?

Mantoux test is tuberculin skin testing with 5 TU of PPD read at 48-72 hours by measuring induration (not erythema). Cutoffs are: greater than or equal to 5 mm in HIV, immunocompromised, recent contacts, or fibrotic lesions on chest X-ray; greater than or equal to 10 mm in high-prevalence populations, healthcare workers, and children under 4 years; greater than or equal to 15 mm in low-risk adults. BCG vaccination can cause false positives up to 15 mm.

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Written by: NEETPGAI Editorial Team Reviewed by: Pending SME Review Last reviewed: April 2026

This article is reviewed by qualified medical professionals for clinical accuracy and exam relevance. For corrections or updates, contact the editorial team.