TB Flashcards
Latent TB
When it gets engulfed, neutrophils try to push through lymphatics, however acid fast are difficult to kill and it stays in the lymphatics
two ways on confirming TB?
- AFB smear then nucleic acid amplification
- culture then DNA probe
You get TB via inhalation into alveoli, after 6-8 weeks of bacterial exposure a small cavitary lesion develops in lower lobes termed primary TB which we always recover from, however it leaves a scar termed Ghon complex. The bacteria are suppressed in the lung lymphatics (latent TB) . 5% chance of this latent TB develop active TB within two years for normal people. HIV pts every year is a 5% chance. Reactivation TB occurs in the upper lobe
Sputum culture done first, if pt cannot then do bronchoscopy
3 sputum cultures on 3 separate days
active vs latent TB on xray
active shows up on xray from lung damage
latent does not show up on xray
Reactivation TB
Represents the most common type of tuberculosis encountered in US, both upper lobes involved
Miliary TB
common in children, pts extremely ill
complications of TB
- bronchiectasis
- solitary tuburculoma
broncholithiasis is a sign of….
chronic TB
healthy person PPD result interpretation
-unless wheal is >15 mm it is considered negative
HIV pt PPD result interpretation
-wheal 5 mm or greater is positive
Any other comorbid condition or abnormal xray result interpretation is
-positive > 10 mm
Quantiferon Gold
- This is a blood test
- Lymphocytes release interferon when exposed to TB bacteria, large amount is positive
- does not distinguish b/w active and latent
ESAT-6 and/or CFP-10 responsiveness detected
M. tuberculosis infection likely
No ESAT-6 or CFP-10 responsiveness detected
M. tuberculosis unlikely
IGRA- interferon gamma release assays
does not distinguish b/w active and latent
