TB

Question 1

Dx of latent TB

Answer 1

Mantoux test

If +ve (or non-reliable) consider interferon gamma testing (eg Quantiferon TB Gold® or T-spot-TB)

Question 2

Dx of active TB

Answer 2

CXR if + –> Sputum MC&S for AFB (acid-fast bacilli resist acid on Ziehl–Neelsen (ZN) staining)

Bronchoscopy and lavage may be needed if no sputum

Question 3

Sputum collection for TB

Answer 3

≥3, with one early morning sample

before starting treatment if possible

Question 4

Histology of TB

Answer 4

Caseating granlumata

Question 5

CXR for TB

Answer 5

Consolidation

cavitation

fibrosis

calcification

Question 6

Mantoux test

Answer 6

aka tuberculin skin test

TB antigen is injected intradermally and the cell mediated response at 48–72h is recorded.

A +ve test indicates immunity

Question 7

Cause of false +ive mantoux

Answer 7

previous exposure

BCG

Question 8

Cause of false -ive mantoux

Answer 8

immunosuppression (miliary TB, sarcoid etc)

Question 9

Why Quantiferon TB Gold and T-spot-TB are better than Mantoux

Answer 9

they measure delayed hypersensitivity reaction, specific to TB

As opposed to just the level of TB antigen with mantoux

Question 10

TB rx timing

Answer 10

Dont wait for culture results

Carry on rx even if culture is -ive, but high clinical suspicion

Question 11

Tests before starting TB rx

Answer 11

Colour vision, Visual acquity (ethambutol causes reversible occular toxicity)

U&E (ethambutol or rifampicin)

Question 12

Initial rx of TB

Answer 12

8 wks

Rifampicin

Isoniazid + pyridoxine (prevent neuropathy)

Pyrazinamide

Ethambutol or streptomycin

Question 13

Continuation phase rx of TB

Answer 13

16 wks

rifampicin

isoniazid