Tuberculosis (TB) and the BCG vaccine

Question 1

What groups should receive the BCG vaccine in the UK

Answer 1

• infants living in TB prevalent areas
• infants with a parent/grandparent from a country where TB is prevalent
• contacts of a case of respiratory TB
• patients who were born/have lived in a TB prevalent country for at least 3 months
• healthcare workers
• prison staff
• those who work with homeless people

Question 2

The TB vaccine is a live attenuated vaccine. TRUE/FALSE?

Answer 2

TRUE
contains live attenuated Mycobacterium bovis

Question 3

Contraindications to a BCG vaccine

Answer 3

previous BCG vaccination
past history of TB
HIV
pregnancy
positive tuberculin test (Heaf or Mantoux)

Question 4

Why is the BCG vaccine not given over the age of 35?

Answer 4

no evidence that it works for people of this age group.

Question 5

Clinical features of Primary TB infection

Answer 5

• may be asymptomatic
• fever
• pleuritic pain (secondary to pleural effusion)
• retrosternal pain (secondary to enlarged bronchial lymph nodes)

Question 6

Clinical features of secondary/reactivated TB

Answer 6

• cough
• productive haemoptysis
• weight loss
• fatigue
• night sweats
• fever

Question 7

Treatment of active TB in initial phase (first 2 months)

Answer 7

Rifampicin
Isoniazid
Pyrazinamide
Ethambutol

Question 8

Continuation phase treatment in TB

Answer 8

Rifampicin
Isoniazid

Question 9

Treatment of latent TB

Answer 9

3 months of isoniazid (with pyridoxine) and rifampicin

OR

6 months of isoniazid (with pyridoxine)

Question 10

For how long are patients with meningeal tuberculosis treated

Answer 10

At least 12 months
(with steroids)

Question 11

In what groups may you use Directly Observed Therapy (3 week dosing regimen)

Answer 11

• homeless people with active TB
• patients likely to have poor concordance
• prisoners with active or latent TB

Question 12

Immune reconstitution disease typically occurs how long after starting TB treatment? How does it present?

Answer 12

• typically 3-6 weeks after starting treatment
• presents with enlarging lymph nodes

Question 13

Adverse effects of rifampicin

Answer 13

potent liver enzyme inducer
hepatitis
orange secretions
flu-like symptoms

Question 14

Adverse effects of Isoniazid

Answer 14

peripheral neuropathy
hepatitis
agranulocytosis
liver enzyme INHIBITOR

Question 15

Adverse effects of pyrazinamide

Answer 15

hyperuricaemia (causing gout)
arthralgia
myalgia
hepatitis

Question 16

How can isoniazid induced peripheral neuropathy be prevented?

Answer 16

pyridoxine (Vitamin B6)

Question 17

Adverse effects of ethambutol

Answer 17

optic neuritis

Question 18

Main technique used to screen for latent TB

Answer 18

Mantoux

in recent years an interferon-gamma blood test has been introduced

Question 19

Describe how a mantoux test is carried out

Answer 19

0.1 ml of purified protein derivative (PPD) injected intradermally

result 2-3 days later

Question 20

Size of induration 2-3 days following Mantoux test:

< 6mm

Answer 20

Negative

=> unvaccinated individuals may be given the BCG

Question 21

Size of induration 2-3 days following Mantoux test:

6 - 15mm

Answer 21

Positive

• Should not be given BCG
• May be due to previous TB infection or BCG

Question 22

Size of induration 2-3 days following Mantoux test:

> 15mm

Answer 22

Strongly positive

• Suggests tuberculosis infection.

Question 23

What causes a false negative mantoux test

Answer 23

miliary TB
sarcoidosis
HIV
lymphoma
very young age (e.g. < 6 months)

Question 24

CXR findings in active TB

Answer 24

• upper lobe cavitation (reactivated TB)
• bilateral hilar lymphadenopathy

Question 25

Investigations used to diagnose TB

Answer 25

• Sputum smear (rapid)
  => Ziehl-Neelsen stain where all mycobacteria are stained (not very sensitive)
• Sputum culture (takes weeks)
  => most sensitive
• Nucleic acid amplification tests (NAAT)

Question 26

Most common site for secondary TB

Answer 26

Lung

Question 27

Sites of extra-pulmonary TB infection

Answer 27

CNS (TB meningitis)
vertebral bodies (Pott’s disease)
cervical lymph nodes
renal
gastrointestinal tract