9. TB Flashcards
Outline the pathophysiology of TB
Transmission = respiratory droplet - coughing, sneezing
Inhaled infectious droplets —> engulfed by alveolar macrophage —> local LN —> primary complex —> 1) PRIMARY - active disease, 2) LATENT = 95% self-cure, 5% reactivated into post primary TB
Miliary = disseminated through bloodstream
Latent = inactive, TST/IFN +ve, CXR normal, cultures -ve, asymp, not infectious
TB disease = active, TST/IFN +ve, CXR abnormal, cultures +ve, symptoms, infectious
Outline the aetiology of TB.
Mycobacterium tuberculosis
Mycobacterium Bovis
Mycobacterium Africanum
M Avium - common in HIV
M Abscessus - common in children with CF
What are the signs and symptoms of TB?
Night sweats
Weight loss - rabid
Cough
Fever
Fatigue
Extrapulmonary TB - LN, larynx, pleura, brain, kidneys, bones and joints
How would you investigate TB?
X-ray = cavitation (not always in the apex), patchy consolidation, fibrosis
Interferon gamma
- does not diff between active and latent
- -ve result doesn’t mean the pt doesn’t have active TB
CT = coin lesion, patchy consolidation
Sputum x3 (C+S) = AFBs acid fast bacillus
Screen for HIV (BBV) = correlation
Bronchoscopy = rule out malignancy
Bronchoalveolar lavage (BAL) smear
PCR for TB DNA
How would you manage TB?
RIPE - rifampicin (urine orange) (cytochrome P450 - interacts with methadone, hormonal contraceptives), isoniazid, pyrazinamide, ethambutol (all 4 for 2 months R+ I for a further 2 months) o Sickness o Feel like arthritis o Itchy o Liver toxicity o Blindness o Peripheral neuropathy
After 2 weeks of treatment you can go back to work
2nd line drugs = Quinolones
Contact tracing = family, work
IGRA = latent TB (does not diff between active and latent)
What are the complications of TB?
Mortality
Lung resection
What are the principles of TB contact tracing?
Identify those who require treatment
Control further spread
Identify genetic evolution of the TB strain
If a patient with TB develops a headache and neck stiffness what might you be concerned about and how would you investigate this further?
Meningitis like symptoms lead me to believe the brain may now be infected with TB
Take a LP sample = C + S for TB
- CT head = ?lesion
How is a diagnosis of Latent TB made and, if confirmed, what treatment should be offered?
Interferon Gamma Releasing Assays (IGRA) = Detection of antigen- specific IFN-gamma production
We do not treat latent TB, 95% will self cure, the further 5% will reactivate at which point we will treat with RIPE. We can also perform risk reduction for the factors that increase the risk of reactivation = alcohol, drug users, malignancy, kidney disease
