Tuberculosis

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Quick Overview

Tuberculosis (TB) is a notifiable infectious disease caused by Mycobacterium tuberculosis, affecting primarily the lungs (pulmonary TB) but can involve any organ system (extrapulmonary TB). NICE NG33 provides comprehensive guidance on diagnosis, treatment, and contact tracing. Key priorities include identifying active disease early, managing latent TB infection (LTBI), and recognizing drug-resistant TB to prevent transmission and complications.

Core Facts & Concepts

Diagnostic Criteria (NICE NG33)

  • Active pulmonary TB: Clinical symptoms + microbiological confirmation (culture/PCR) OR radiological evidence + clinical response to treatment
  • Latent TB: Positive interferon-gamma release assay (IGRA) or tuberculin skin test (TST ≥6mm if BCG vaccinated, ≥5mm if not) WITHOUT active disease
  • Microbiological confirmation: Sputum smear (Ziehl-Neelsen stain), culture (gold standard, 2-6 weeks), or nucleic acid amplification test (NAAT, results in 24-48 hours)

Figure 1: Chest X-ray showing upper lobe cavitation and patchy consolidation

First-Line Treatment Regimens

  • Standard 6-month regimen (drug-sensitive TB):

    • Intensive phase (2 months): RIPE daily
      • Rifampicin 10mg/kg (max 600mg)
      • Isoniazid 5mg/kg (max 300mg) + pyridoxine 10mg
      • Pyrazinamide 25mg/kg (max 2g if <50kg, 2.5g if ≥50kg)
      • Ethambutol 15mg/kg
    • Continuation phase (4 months): RI daily
  • CNS/bone/joint TB: Extend continuation phase to 10 months (12 months total)

  • Pyridoxine supplementation: Mandatory with isoniazid (prevents peripheral neuropathy)

Drug-Resistant TB Recognition

  • Risk factors: Previous TB treatment, contact with drug-resistant case, birth/residence in high-prevalence area
  • Send rapid molecular testing (e.g., GeneXpert for rifampicin resistance)
  • MDR-TB: Resistant to rifampicin + isoniazid (requires specialist management, 18-24 month regimens)

Problem-Solving Approach

Step-by-Step Diagnostic Pathway

  1. Clinical suspicion: Persistent cough >3 weeks, fever, night sweats, weight loss, haemoptysis
  2. Initial investigations:
    • Chest X-ray (upper lobe infiltrates, cavitation, lymphadenopathy)
    • Three sputum samples (early morning) for smear, culture, and NAAT
    • HIV test (mandatory in all TB cases)
  3. Extrapulmonary TB: Sample appropriate site (pleural fluid, CSF, lymph node biopsy)
  4. LTBI screening indications:
    • Close contacts of active TB cases
    • Immunosuppression planned (anti-TNF, transplant)
    • Healthcare workers, migrants from high-prevalence countries

Figure 2: Ziehl-Neelsen stain showing acid-fast bacilli

🚩 Red Flags Requiring Urgent Action

  • Smear-positive pulmonary TB → respiratory isolation immediately
  • CNS TB → dexamethasone 0.4mg/kg daily (reduces mortality)
  • Drug-resistant TB suspected → specialist referral same day
  • HIV co-infection → start ART within 2-8 weeks of TB treatment

Analysis Framework

FeatureActive TBLatent TB
SymptomsPresent (cough, fever, weight loss)Absent
Chest X-rayAbnormalNormal
Sputum/culturePositiveNegative
IGRA/TSTUsually positivePositive
Treatment duration6-12 months (RIPE → RI)3 months (rifampicin + isoniazid) OR 6 months (isoniazid alone)
InfectivityContagious (if pulmonary, smear-positive)Non-infectious

Contact Tracing Protocol (NICE NG33)

  • Close contacts: Screen with IGRA/TST and chest X-ray
  • Timing: Test at initial contact; if negative and immunocompetent, repeat at 8 weeks
  • Offer LTBI treatment if positive screening and active TB excluded

Visual Aid

Key Points Summary

Standard treatment: 2 months RIPE (rifampicin 10mg/kg, isoniazid 5mg/kg + pyridoxine, pyrazinamide 25mg/kg, ethambutol 15mg/kg) → 4 months RI

Extend to 12 months total for CNS, bone, or joint TB

LTBI treatment: 3 months rifampicin + isoniazid OR 6 months isoniazid alone (prevents progression to active disease in 60-90%)

Drug-resistant TB risk factors: Previous treatment, contact with resistant case, high-prevalence country origin → send rapid molecular testing

Contact tracing: Screen close contacts with IGRA/TST + chest X-ray; repeat at 8 weeks if initially negative

Mandatory notifications: Report all TB cases (active and LTBI treated) to local Health Protection Team within 3 days

Directly observed therapy (DOT): Consider for non-adherence risk, homelessness, substance misuse, MDR-TB

⚠️ Warning: Never use monotherapy (risks resistance development). Always check HIV status and ensure pyridoxine supplementation with isoniazid.

Practice Questions: Tuberculosis

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Flashcards: Tuberculosis

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Women who are HIV positive should be offered _____ cervical cancer screening

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