TB DSA Flashcards
As immunity to Mycobacterium TB develops, how does the patient react to the tuberculin skin test (TST) and the interferon-y release assay (IGRA)?
Positive
If the TB infection is contained, a person is said to be what?
In a state of latent TB infection (LTBI), without systemic manifestations, however the risk for reactivation remains for years.
Reactivation TB is usually localized to the _____.
Lungs
What are risk factors for primary progression and reactivation of quiescent TB?
- HIV/AIDS***
- Malnutrition
- Immunosuppressed states
What form the cornerstone of control of active TB infection?
- Agressive screening
- High amount of suspicion
How can we promote primary and secondary prevention of TB?
- Primary: isolate (in hospital, put in room with (-) air pressure and all entering people should have masks with filtering capacity of 95%)
- Secondary: treat patients with suspected LTBI
ALL high-risk patients with + TST/IGRA should be offered _______, unless prior treatment is noted or medically contraindicated.
LTBI treatment
Who is screening for TB performed for and via what methods?
- Screening is NOT needed for low-risk indiviuals.
- High risk of exposure or contraction: Mantoux TST or IGRA
A (+) TST is defined by _________
the diameter of the indurated area, considering risk profile.
Induration >5mm is postive for whom?
- HIV infection
- Recent contract with case of active TB
- Person with fibrotic changes changes on CXR that show old TB
- Organ transplant/immunosupressed.
Induration >10mm is postive for whom?
- Immigrant from country with high TB prevelance within 5 yrs
- IV drug user
- Person who works are high-risk congregate area
- Health care worker, child under 4 YO or expossed to adult
Induration >15mm is postive for whom?
Person w no risk factors for TB
Why should re-testing or empiral treatment be done for high risk patients (ex. those with HIV)?
Skin test results may not become + for 12 weeks after exposure to active infection.
When should two-step testing be performed and why?
- Pt exposed to TB in the distant past could have a (-) skin test.
- Thus, a second test done 7-21 days after first can help reduce false (-) response rate => uncover a true positive.
- Perform at regular testing programs (nursing home, hospital)
How is IGRA different from TST?
What population is it preferred for?
- IGRA asses T-cell response to M. TB.
- More expensive, but done in a single blood draw and no need to come back.
- Does not give a false postive in person w BCG vaccine
- Preferred for: person w BCG vaccine and those unlikely to return for TST interpretation,
What test is preffered for children UNDER 5 YO?
TST
IGRA and TST are used separtely.
In what specific situations are they performed separetly?
- Initial test is is indeterminate or (-), but high clinical suspicion.
Which test can differentiate between LTBI and active TB?
Neither
If IGRA or TST is (+), how do we determine is patient has active TB or LTBI?
CXR, hx, PE
Patients with pulmonary TB, often have what sx?
ASYMPTOMATIC.
Constitutional symptoms, as well as local sx (cough) can develop.
The most common pulmonary finding in patients with active tuberculosis is
Normal examination
HIV or immunocompromised TB patients will …
- have a greater liklihood of dissemination/extrapulmonary infection
but classic sx of TB are absent and CXR may be NL
What are the differential dx of TB?
- Non-TB mycobacterial infection: perform CT
- Sarcoidosis
- Aspiration pneumonia
- Lung abscess
- Histoplasmosis cocidiodomycosis
- Wegners
- Actinomycosis
- Lung cancer
What is the cornerstone of management of TB?
- 1. Bacteriologic confirmation
- 2. Susceptibility testing
