Tuberculosis

Question 1

What causes TB?

Answer 1

Airborne infection by Mycobacterium tuberculosis.

Question 2

How many people can one infectious case infect per year?

Answer 2

10–15 people.

Question 3

What stain is used to identify TB microscopically?

Answer 3

Acid-fast stain (AFB – red rods).

Question 4

What fluorescent stain can be used?

Answer 4

Auramine stain.

Question 5

What is the hallmark pathological lesion of TB?

Answer 5

Granuloma.

Question 6

What are the four pillars of TB diagnosis?

Answer 6

• Clinical suspicion
• Risk factors
• Radiology
• Microbiology

Question 7

High-risk settings for new TB infection?

Answer 7

• Prisons
• Nursing homes
• Homeless shelters
• Healthcare settings
• Substance misuse
• Immigrant centres

Question 8

Biological risk factors for progression?

Answer 8

• Extremes of age
• Pregnancy
• Genetic factors
• Apical fibronodular changes

Question 9

Medical risk factors?

Answer 9

• HIV
• Diabetes
• Renal failure
• Silicosis
• Malnutrition
• Smoking
• Cancer
• Transplant
• Alcohol/drug misuse

Question 10

Social risk factors?

Answer 10

• Homelessness
• Immigration
• Incarceration
• Social isolation

Question 11

What proportion of TB in UK is imported/reactivation?

Answer 11

> 60%.

Question 12

% of TB that is pulmonary?

Answer 12

~75%.

Question 13

% that is extra-pulmonary only?

Answer 13

~18%

Question 14

Most common site of extra-pulmonary TB?

Answer 14

Lymph nodes (~41%).

Question 15

Other common extra-pulmonary sites?

Answer 15

• Pleural
• Bone/joint
• GU
• Meningeal

Question 16

Typical location of pulmonary TB?

Answer 16

Apical/posterior segments of upper lobes.

Question 17

Typical infiltrate pattern?

Answer 17

Fibronodular shadowing ± cavitation.

Question 18

Cavity characteristics?

Answer 18

Thick irregular walls; air-fluid levels uncommon.

Question 19

What happens to lung volume?

Answer 19

Progressive volume loss.

Question 20

Atypical radiological features (~30%)?

Answer 20

• Lower zone disease
• Effusion
• Mass lesion
• Miliary pattern
• Normal CXR

Question 21

What confirms TB diagnosis?

Answer 21

Positive culture for M. tuberculosis.

Question 22

Should cultures be done if smear is negative?

Answer 22

Yes — always.

Question 23

How long does liquid culture (e.g., BACTEC) take?

Answer 23

4–14 days.

Question 24

What is Xpert MTB/RIF (CEPHAID)?

Answer 24

PCR test detecting TB DNA + rifampicin resistance (results in ~90 mins).

Question 25

What is genome sequencing used for?

Answer 25

Susceptibility prediction.

Question 26

What defines MDR-TB?

Answer 26

Resistance to isoniazid and rifampicin.

Question 27

Who is at increased risk of drug resistance?

Answer 27

* Previous TB treatment * Contact with MDR case * From high MDR-prevalence areas * Persistent positive cultures after 2 months * Inadequate prior treatment

Question 28

First step?

Answer 28

Isolate patient.

Question 29

What samples are required?

Answer 29

3 sputum samples (8–24 hours apart).

Question 30

When use rapid DNA testing?

Answer 30

If MDR risk or rapid diagnosis required.

Question 31

What other tests should be offered?

Answer 31

HIV and Hepatitis testing.

Question 32

Who needs contact tracing?

Answer 32

* New arrivals * Household contacts * ≥8 hours exposure to smear-positive case

Question 33

Examples of IGRA tests?

Answer 33

Quantiferon TB Gold, T-Spot.

Question 34

What do they measure?

Answer 34

IFN-γ release from T-cells in response to TB antigens.

Question 35

Are they affected by BCG vaccination?

Answer 35

No.

Question 36

Main use of IGRA?

Answer 36

Screening for latent TB.

Question 37

Four first-line drugs?

Answer 37

* Isoniazid * Rifampicin * Pyrazinamide * Ethambutol

Question 38

Why combination therapy?

Answer 38

Prevent resistance.

Question 39

Which drugs are bactericidal?

Answer 39

INH & RIF.

Question 40

Which drugs have sterilising activity?

Answer 40

RIF & PZA.

Question 41

Mechanism? Isoniazid

Answer 41

Blocks mycolic acid synthesis.

Question 42

Main adverse effects? Isoniazid

Answer 42

Hepatitis, peripheral neuropathy.

Question 43

Mechanism? Rifampicin

Answer 43

Inhibits DNA-dependent RNA polymerase.

Question 44

Major issue? Rifampicin

Answer 44

Induces CYP450 (drug interactions).

Question 45

Apical cavitating lesion + weight loss + night sweats = ?

Answer 45

Pulmonary TB.

Question 46

TB + HIV = ?

Answer 46

High risk of progression.

Question 47

IGRA positive but asymptomatic = ?

Answer 47

Latent TB.

Question 48

Optic neuritis during TB treatment = ?

Answer 48

Ethambutol toxicity.