TB Flashcards
Pathophysiology
Caused by mycobacterium tuberculosis
Can be asymptomatic as lies dormant but reactivated in later life
Geographical distribution
Asia
Africa
South America
Transmission
Aerosol inhalation causing pulmonary infection which can spread haematogenously
Screening tools
Quantiferon test
T spot
CXR
Quantiferon test
Assesses amount of interferon gamma released by T cells when exposed to a protein found in mycobacterium tuberculosis
- pre-exposed cells produce more
- does not differentiate between active and latent
- not diagnostic
T spot test
Isolates lymphocytes so can be used if pt is lymphocyte deficient
Who is screened
Immigrants from high prevalence countries
Healthcare workers
HIV positive patients
Patients starting immunosuppressants
Treatment of latent TB
3 months rifampicin and isoniazid
OR
6 months rifampicin alone
Contraindications for treating latent Tb
Over 35 yrs old
- increased risk of hepatotoxicity
Presentation of active TB
Fever Night sweats Weight loss Haemoptysis Persistent cough
Signs
Temperature Pleural effusion can cause: Crepitations Bronchial breathing Possible pericardial rub
Other signs may be present:
- clubbing
- cachexia
- lymphadenopathy
- hepatomegaly
- erythema nodosum
Investigations
Obs
Bloods - FBC, U+Es, LFTs, CRP
CXR - cavitation, pleural effusion
CT - lymphadenopathy with central necrosis
Sputum culture (gold standard) - can take 6 weeks
Sputum sample smear negative
Bronchoscope +/- endobronchial USS guided biopsy of lymph nodes
Histology findings
Casseating granulomas
Langhans giant cells
How to get sample with different TB types
Meningeal TB - lumbar puncture
Military TB - lumbar puncture and sputum
Lymph node - core biopsy of lymph node
Pericardial - pericardiocentesis
Gastrointestinal -colonoscopy and bowel biopsy
