TB

Question 1

What is the epidemiology of TB?

Answer 1

Lots of people affected in subsaharan Africa; also abundance in India

13.5/100,000/year - incidence UK - most people of Indian and Pakistani and African heritage

London, West Midlands focal points

Risk factors:
Strong association with HIV 
DM - 3x the risk, also worse prognosis 
Malnutrition
Smoking, harmful alcohol use (esp for treatment adherence)
Immunodeficiency - transplant recipients, neonates 
Homelessness 
IVDU

Question 2

What is the aetiology and pathophysiology of TB ?

Answer 2

Mycobacterium tuberculosis

• Impervious to gram stains, hence other media needed
• Aerobe

Aerosol - lung-lung, spitting/sneezing

Can also be caught by drinking infected unpasteurised cows milk (though you get abdominal TB not pulmonary)

Majority of people can mount an effective immune response and encapsulate the organism forever
95% do not have the disease

Primary pulmonary disease:

• Granuloma forms at site of bacterial lodging
• Bacilli taken up in lymphatics to hilar lymph nodes
• Granuloma enlarges - develops cavity (coin shaped lesion) - may breach airway - coughing - transmission of TB

Extra pulmonary TB:

• Dissemination via blood vessels that have been eroded into - infection spreads
• Lymph node, CNS (TB meningitis), pleural, bone/joint, abdominal, genitourinary, miliary TB - lots of lesions EVERYWHERE
• Symptoms relate to mass effect and local erosion

Latent TB:

• Post primary disease
• Reactivation of TB at a later date after initial infection
• Symptoms depend on location of lodging

Can also be re-infected:
- Completely new disease

Question 3

How does TB present ?

Answer 3

Slow progression of symptoms - distinguishing from other infections

Systemic:

• Weight loss*
• Night sweats*
• Low grade fever
• Anorexia
• Malaise

Pulmonary TB:

• Cough +/- haemoptysis
• Chest pain
• SOB

Question 4

How do yo investigate TB?

Answer 4

CXR:

• Consolidation - often apical
• ‘coin shaped’ granuloma lesion
• Hilar lymphadenopathy
• Pleural effusion

Sputum cultures:

• 3x early morning cultures
• May need to be induced i.e. with nebulised saline or bronchoscopy with lavage
• Ziehl-Nielsen (ZN) stain for acid-fast bacilli - takes 3-12weeks…

Other samples:

• Urine, CSF, Pleural fluid, Biopsy
• Depending on suspected seeding site of TB
• All for histopathology

Genetic sequencing
- Can give faster results for sensitivities (previous methods using cultures took weeks)

Latent TB:

• +ve screening test e.g.
  1) Mantoux/tuberculin skin test = PPD tuberculin injected, +ve for latent TB if forms a small hard red bump at injection site 48-72hrs post test; possible false -ve in immunocompromise and false +ve in previous BCG vaccine, therefore:
  2) Interferon gamma release assay - e.g. T-SPOT; but cannot distinguish between active and latent infection

___

Other possible bloods:

• FBC - WCC
• CRP - raised
• Cultures
• Hypoalbuminaemia
• Hypergammaglobulinaemia
• Hypercalcemia - granulomas produce hormones that promote calcium

Question 5

What is the pharmacological management of TB?

Answer 5

RIPE (ONAO)

Rifampicin - 6/12 - Enzyme inducer (oral contraceptives reduced efficacy); SE: orange secretions/excretions
+
Isoniazid - 6/12 - SE: neuropathy (need to take B6 supplements)
+
Pyrazinamide - 2/12 - SE: arthralgia
+
Ethambutol - 2/12 - SE: optic neuritis

If sensitivities suggest; if not discuss with micro

Adherence is essential - will feel better after a couple of weeks but whole course needs completing else increased risk of multidrug resistant TB = bad and common (1/100 cases)

Directly Observed Therapy = DOTs - people need to be watched taking the drugs

Also a community TB nursing team

Possible corticosteroids for CNS and pericardial TB

Question 6

How do you prevent TB?

Answer 6

Isolation of suspected or confirmed cases:

• Negative pressure room with barrier nursing/masks etc until 3 sputum samples have been urgently tested = ‘smears’ - must remain isolated if +ve
• Smears repeated 2wks post finishing Tx - should be clear

Active case finding

• Contact tracing
• Is a notifiable disease too

Detection and treatment of latent TB

Vaccination - BCG, live vaccine - given at birth to anyone with high risk (family from endemic area, family visit endemic areas)