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
In patients with infection, TST is usually positive within ________ hours.
48-72
Which patients with active TB can show a false-negative?
- Anergic patients
- 25% of patients with active TB
What tests should be run on a patient suspected of ACTIVE TB?
- Acid-fast bacili smear
- Cultures of pulmonary and suspected site of infection
- CXR
- TST or IGRA
What test can be formed to exclude TB in patients with false (+) sputum or to confirm TB in some patients with false (-) smears?
Nucleic acid amplication test of sputum
What is the gold standard used for diagnosis of TB?
Solid media culture + liquid media culture
What test is run for patients suspected of pleural TB?
thoracentesis or pleural biopsy
On radiology, what does reactivation of TB look like?
Lesions in the apical posterior segments of the upper lung and superior segments of the lower lobe
What can we see on radiology for patients with
- Primary progressive TB
- immunocompromised pts
- Hilar adenopathy or infiltrates in any part of lung
- Atypical or absent findings
What is the standard treatment for suspected or confirmed active TB?
RIPE (rifampin, isoniazid, pyrazinamide and ethambutol) for 6 months.
How can we monitor treatment administered to patients with suspective/active TB infection?
- Repeat suptum smear and culture after 2 month phase, to determine whether patient should continue for 4 months or 7 months.
- MDR TB is resistant to
- Extensively drug-resitant TB (XDR) is resistant to
- Isoniazid and rifampin
- Isoniazid and rifampin + fluoroqinolones and at least kanamycin, amikacin or capreomycin.
How do we treat MDR or XDR?
Individualized regimen based on comphrensive drug susceptilbilty and consutation with a expert.
How are patients with LTBI treated?
Individualized:
- Isoniazid/day/ 9 months
- Rifampin/day/4 months
- Rifapentine + isonizid/1wk/3months via directly observed therapy.
B4 tx: exclude active TB, risk and benefits, obtain blood tests to test for drug toxicities that may complicate tx.
How should we follow up with TB patients
Careful monitoring
- Monthly sputum cultures
- Adjust drugs
- Contact TB expert if sputum culture remains positive or if pt has not improved clinically after 3 months.
- Periodic assessments for adverse reactions
