Tuberculosis

Question 1

What is the causative organism of TB?

Answer 1

Mycobacterium TB

Question 2

What are the options that can occur on TB exposure?

Answer 2

Immediate clearance
Primary disease: Onset of active disease
Latent infection- Infection is contained and suppressed by the immune system. This can then re-activate to cause secondary infection

Question 3

What are some symptoms of primary TB infection?

Answer 3

Haemoptysis
Night sweats
Fever
Weightloss
Fatigue

Question 4

What might cause reactivation of latent TB?

Answer 4

Immunosupression
Anti TNF therapy
HIV

Question 5

What investigation is done for TB?

Answer 5

Sputum culture- ZN/AFB staining, TB culture
Tuberculin Skin Test- Shows exposure to BCG or TB (therefore indicates latent TB too)
Interferon gamma release assay- more specific to TB
CXR- Apical cavitating nodules, effusions, hilar lymphadenopathy
If no sputum- may induce sputum or BAL

Biopsy of extrapulmonary sites- Caseating granulomas

ALWAYS DO A HIV TEST (REACTIVATION OCCURS WITH IMMUNOSUPPRESSION)

Question 6

What might be seen on CXR for TB?

Answer 6

Upper lobe cavitating masses
Hilar lymphadenopathy
Pleural effusion

Question 7

What are the majority of cases of active TB due to?

Answer 7

Reactivation in a patient with latent TB

This can occur with immunosuppression, HIV, anti TNF therapy

Question 8

What is miliary TB?

Answer 8

Widespread TB that has spread via haematogenous spread. Causes milliarly seeded appearance on a CXR

Question 9

What type of granuloma is seen in TB?

Answer 9

Caseating granuloma

Note non-caseating granulomas are seen in sarcoidosis.

Question 10

Outside of the lungs where the other two most common places for TB to infect?

Answer 10

Lymph nodes
Gastrointestinal system

CNS and bone infection also common.

Question 11

What is the treatment for active pulmonary TB?

Answer 11

Rifampicin
Isoniazid
Pyrazinamide
Ethambutol

6 months of top two
2 months at start with all four

Question 12

What is a Ghon focus?

Answer 12

This is where the caesiating granuloma is

Question 13

What is a Ghon complex?

Answer 13

Ghon focus and the lymph node involved with caseating granuloma

Undergo fibrosis and calcification making them visible on the CXR

Question 14

What does TB cause with renal involvement?

Answer 14

Sterile pyuria

Question 15

What does TB cause with adrenal gland involvement?

Answer 15

Addisons

Question 16

What does the tuberculin skin test show?

Answer 16

It shows prior exposure to TB therefore may indicate active or latent TB
Immune reaction occurs within 48-72 hours

Question 17

What test can be done to test for exposure to TB?

Answer 17

Tuberculin skin test

Interferon Gamma Release Assays (Blood test)

Question 18

How long is rifampicin and isoniazid give for?

Answer 18

6 months

Question 19

How long are ethambutol and pyrazinamide given for?

Answer 19

2 months

Question 20

How might samples be obtained for AFB/ZN staining or TB culture?

Answer 20

Sputum
BAL
Induced sputum- nebulised salbutamol

Biopsy

Question 21

What should you also test for in patients with TB?

Answer 21

HIV

Question 22

What are some side effects of rifampicin?

Answer 22

Liver toxicity
Renal failure
Thrombocytopenia

Question 23

What are some side effects of isoniazid?

Answer 23

Peripheral neuropathy

Liver toxicity

Question 24

What are some side effects of pyrazinamide?

Answer 24

Liver toxicity

Question 25

What are some side effects of ethambutol?

Answer 25

Rarely causes optic toxicity so baseline visual acuity should be checked.

Question 26

Why is BCG vaccination contraindicated in HIV positive patients?

Answer 26

It is a live vaccine

Question 27

If a patient is diagnosed with active TB what needs to be done?

Answer 27

Contact tracing | Test all family members, colleagues, classmates

Question 28

Where should patients with suspected TB be kept in a hospital?

Answer 28

In side rooms FFP3 face masks must be used when seeing them as well as standard PPE.

Question 29

How can you test for latent TB?

Answer 29

Tuberculin skin test | Interferon gamma release assay

Question 30

Why does latent TB occur?

Answer 30

Immune system prevents primary infection but this is done through granuloma formation where the mycobacterium are walled off to prevent spread. Granulomas are maintained with TNF alpha.

Question 31

Who should be tested for latent TB?

Answer 31

Contacts of people with active TB New healthcare workers Immunocompromised patients New entrants from high incidence countries

Question 32

How is latent TB treated?

Answer 32

Isoniazid and rifampicin daily for 3 months This reduces risk of reactivation later on