What is the classical presentation of TB?
- young, recent travel abroad (South Asia)
- acute SOB, pleuritic chest pain
- signs of infection
What findings on CXR indicate TB?
- Ranke complex (ghon complexes at hilum - subpleural/LL fibrosis & calcification)
- pleural effusion
What would be found on a diagnostic aspirate in TB?
Acid-fast bacilli
Which stains show acid-fast bacteria on histology?
Auramine-O stain
Ziehl-Neelsen stain
What are acid-fast bacteria?
Bacteria resistant to decolourisation when acid is added.
How does mycobacterium tuberculosis appear on cytology?
Rod-shaped bacillus
How is TB transmitted?
Droplets
Who is at risk of latent TB?
Immunocompromised patients (AIDS, ageing, recent ChTx)
How does caseous necrosis cause systemic miliary TB? (SMTB)
Oxygenation greatest in upper lobes
- Tm cells release cytokines =
- caseous necrosis
- cavitation & allows dissemination of TB
To lungs: bronchopneumonia
To vasc: SMTB
How does SMTB present?
Head - meningitis
Neck - cervical lymphadenitis (scrofula)
Lumbar spine - Pott disease
Liver - Hepatitis
Adrenals - Addison’s
Renal - sterile pyuria (WBCs in urine)
What is the Mantoux skin test for TB?
- tuberculin intradermal injection = immune reaction (48-72h)
+ve (large area induration) = previous/exposed
What is the IFN-y release assay? (IGRA)
Specific blood test to TB (unlikely to be false +ve from BCG vaccine)
If the IGRA or the Mantoux skin test produce a +ve result, what is the next appropriate step in the investigation of TB?
CXR
What are the red flag symptoms of TB?
- fever, night sweats, chills
- UWL
- haemoptysis
What lab work can be done to diagnose TB in symptomatic individuals?
- sputum culture
- bronchoalveolar lavage (stain, culture, PCR)
How is latent TB treated?
Isoniazid (9m)
How is active TB treated?
Combination of:
- isoniazid
- Rafampin
- ethambutol
- pyrazinamide
How should reactivated TB be managed?
(Very infectious!)
- negative pressure rooms
- visitors N-95 masks (95% aerosols)
How must management be different for MDR and XDR-TB?
- target strains with abx
- use multiple abx in combination
- complete full abx course
(?pretomanid, bedaquiline, linezolid)
How long do granulomas take to form after primary infection with TB?
3w
