Tuberculosis

Question 1

When should latent TB be looked for? (3)

Answer 1

If someone:
Is a recent contact to an infectious case of pulmonary TB
Is about to be started on immunosuppresive medication
Has recently emigrated to the UK from a country with a high incidence of TB

Question 2

What are the four key steps to diagnosing latent TB?

Answer 2

Perform a TB immune memory test (Tuberculin Skin Test/ Mantoux test)
Take a history to assess the exposure risk
Chest X-ray
Rule out active TB

Question 3

What is the immune memory test for LTBI?

Answer 3

T-cell memory test
Expose circulating T cells to proteins from M tuberculosis bacilli. If memory T cells for TB exist they will produce interferon gamma (IFNy)
IFNy responses can be detected by a reaction in the skin or in a laboratory.

It is not possible to detect dormant bacteria so immune memory response is detected.

Question 4

Describe the Mantoux test.

Answer 4

Mtb protein is injected interdermally
stimulates Mtb specific memory T cells
Is read after 48 hours by the size of the area of induration
Does not distinguish between LTBI or active TB

Question 5

What is an alternative to the Tubereculin Skin Test?

Answer 5

Interferon gamma release assays (IGRAs)

Less sensitive than Mantoux test

Question 6

How is active TB ruled out?

Answer 6

Active TB is unlikely without systemic or local features

Question 7

What are the systemic features of TB?

Answer 7

Weight loss*
Low grade fever
Anorexia
Night sweats*
Malaise
Enlarged Lymph Nodes
* most predictive of TB

Question 8

What are the pulmonary features of TB?

Answer 8

Cough
Sputum
Haemoptysis
Chest pain

Prolonged >3 weeks of lower respiratory tract symptoms and a lack of response to routine antibiotics

Question 9

What are the chest x-ray features of TB?

Answer 9

Hilar lymph nodes
Apical lobe consolidation
Cavities

Question 10

What are the population exposure risks of TB?

Answer 10

• From a high TB incidence country
• Grew up in the UK before 1970s when TB incidence was still high
• Prolonged visit to a country with high TB incidence

Question 11

What are the individual exposure risks of TB?

Answer 11

• Previous history of TB
• History of close contact with pulmonary TB case
• Historical exposure to unpasteurised cow’s milk (Bovine TB - M.bovis)
• Occupational risk e.g. some types of health care worker

Question 12

Why should a chest x-ray be performed in latent TB?

Answer 12

To rule out active pulmonary TB.

To show evidence of old TB infection that never caused recognised disease

Question 13

How can latent TB be excluded?

Answer 13

No single latent TB test is 100% accurate

To exclude LTBI in someone with risk factors, the TST, IGRA and CXR should all be negative or normal

Question 14

What is the implication of latent TB?

Answer 14

Of 100 people exposed to TB:
90 may have LTBI but will never develop TB
5 develop active TB within 2 years of exposure
5 develop active TB at some stage later in their lifetime

Question 15

What increases the risk of LTBI developing into TB?

Answer 15

Immunosuppression
Pregnancy
Older age
HIV

Question 16

What is the chemoprophylaxis for LTBI?

Answer 16

Either 6 months of Isoniazid
3 months of Rifampicine + Isoniazin combination therapy

Is about 66% effective

Question 17

What are some of the side effects of LTBI?

Answer 17

Rifampicine
Red urine
Hepatitis 1%
Drug Interactions

Isoiazid
Hepatitis 1%
Peripheral nephropathy 1%

Question 18

What drug change must be made if chemoprophylaxis for LTBI is prescribed?

Answer 18

Alternatives to hormonal contraceptives will be required

Question 19

What are the investigations for active TB?

Answer 19

Sputum smear microscopy for acid fast bacilli
(instant result 80% sensitive)

Sputum culture
Confirms species of Mtb
>90% sensitive but takes 2-3 weeks

Chest X-ray

Question 20

What contacts are at risk of TB and may need to be traced?

Answer 20

Same household
Work colleagues
Patients in hospitals or care homes
(requires hours of contact)

Question 21

What are the notification requirements for TB?

Answer 21

Notify PHE

In hospital inform - infection prevention and control team

Question 22

What is the treatment for active TB?

Answer 22

RIPE
Rifampicine - red urine
Isoniazid - neuropathy
Pyrazinamide - hepatitis, gout
Ethambutol - optic neuritis

Treat for 6 months total
2 months of RIPE
+ 4 months of RI

Vitamin B6 should be given to prevent neurotoxisity

Question 23

Medication information for active TB treatment?

Answer 23

GI side effects and nausea common
Large tablet burden
Anti-emetics may be required
Rifampicine absorption best on an empty stomach

Question 24

What other healthcare professionals may be involved?

Answer 24

It can be challenging and TB nurses will be offered to help keep people on track

Question 25

What happens with people’s work?

Answer 25

Must be off work with active TB.
When treatment is commenced approximately 4 weeks will be required until sputum is not being produced.
Contact tracing may be required.