Tuberculosis

Question 1

What is the classical presentation of TB?

Answer 1

• young, recent travel abroad (South Asia)
• acute SOB, pleuritic chest pain
• signs of infection

Question 2

What findings on CXR indicate TB?

Answer 2

• Ranke complex (ghon complexes at hilum - subpleural/LL fibrosis & calcification)
• pleural effusion

Question 3

What would be found on a diagnostic aspirate in TB?

Answer 3

Acid-fast bacilli

Question 4

Which stains show acid-fast bacteria on histology?

Answer 4

Auramine-O stain

Ziehl-Neelsen stain

Question 5

What are acid-fast bacteria?

Answer 5

Bacteria resistant to decolourisation when acid is added.

Question 6

How does mycobacterium tuberculosis appear on cytology?

Answer 6

Rod-shaped bacillus

Question 7

How is TB transmitted?

Answer 7

Droplets

Question 8

Who is at risk of latent TB?

Answer 8

Immunocompromised patients (AIDS, ageing, recent ChTx)

Question 9

How does caseous necrosis cause systemic miliary TB? (SMTB)

Answer 9

Oxygenation greatest in upper lobes
- Tm cells release cytokines =
- caseous necrosis
- cavitation & allows dissemination of TB
To lungs: bronchopneumonia
To vasc: SMTB

Question 10

How does SMTB present?

Answer 10

Head - meningitis
Neck - cervical lymphadenitis (scrofula)
Lumbar spine - Pott disease
Liver - Hepatitis
Adrenals - Addison’s
Renal - sterile pyuria (WBCs in urine)

Question 11

What is the Mantoux skin test for TB?

Answer 11

• tuberculin intradermal injection = immune reaction (48-72h)

+ve (large area induration) = previous/exposed

Question 12

What is the IFN-y release assay? (IGRA)

Answer 12

Specific blood test to TB (unlikely to be false +ve from BCG vaccine)

Question 13

If the IGRA or the Mantoux skin test produce a +ve result, what is the next appropriate step in the investigation of TB?

Answer 13

CXR

Question 14

What are the red flag symptoms of TB?

Answer 14

• fever, night sweats, chills
• UWL
• haemoptysis

Question 15

What lab work can be done to diagnose TB in symptomatic individuals?

Answer 15

• sputum culture
• bronchoalveolar lavage (stain, culture, PCR)

Question 16

How is latent TB treated?

Answer 16

Isoniazid (9m)

Question 17

How is active TB treated?

Answer 17

Combination of:
- isoniazid
- Rafampin
- ethambutol
- pyrazinamide

Question 18

How should reactivated TB be managed?

Answer 18

(Very infectious!)
- negative pressure rooms
- visitors N-95 masks (95% aerosols)

Question 19

How must management be different for MDR and XDR-TB?

Answer 19

• target strains with abx
• use multiple abx in combination
• complete full abx course

(?pretomanid, bedaquiline, linezolid)

Question 20

How long do granulomas take to form after primary infection with TB?

Answer 20

3w