TB Flashcards
1
Q
what is TB bact
A
mycobacterium
- special cell envelope
- leads to it being acid fast - doesn’t show up on gram stain
- grows slowly - slow cultures
2
Q
how is TB transmitted
A
ppl with pulmonary or laryngeal aerosolize
- local defences can destroy if it doesn’t get too deep
3
Q
what happens if gets into alveoli
A
- cell mediated immunity creates a granuloma
- person now has latent TB
4
Q
what is chance of going active
A
10% will go active
50% of those in 2 year
- most TB in world is reactivated
5
Q
what is TB in toronto
A
from immigrants
6
Q
2 ways to test latent
A
- skin test - TST
2. interfereon gamma release assay - IGRAS
7
Q
3 ways to diagnose active
A
- acid fast bacilli and cultures
- path consisitent with necrotizing granulomas
- clinical presentations
8
Q
what is TST
A
- glyscerol extract of TB is put in skin
- read 48-72 hours later
9
Q
what is IGRA
A
- tests to see if WBCs from infected patient will release IFN-g when mixed with antigens from TB
10
Q
how does TST and IGRA compare
A
- IGRA are more specific than TST if previus BCG given
- neither can separate latent from active
- IGRA more specific for TB versus other non TB bacterium
11
Q
3 parts of interpreting TST
A
- size of induration
- PPV
- risk of disease if truly infected
12
Q
3 levels and situations that would be considered pos.
A
0-4
- normal, but for children
13
Q
2 things that PPV is confounded by on TST
A
- previous BCG - after 1yo
- previous NTM
- found in soil and such stuff
14
Q
7 things that make a person high risk
A
- AIDS
- HIV
- tranplant
- silcosis
- chronic renal failure
- carcinoma of head
- recent TB
15
Q
7 things that make increased risk
A
- steroid tx
- TNF-a is
- diabetes
- underweight
- young when infected
- smoker
- granuloma
