Flashcards in TB Deck (46)
Why is such long treatment regimen needed for TB?
-granuloma blocks ABX
-organism is slow growing
What is MDR TB?
resistant to INH and RIF (common in AIDs patients)
What is XDR TB?
resistance to INH, RIF, fluoroquinolone, and at least 1 other drug
How does HIV affect TB?
-increased frequency of false negative sputum smears
-absence of granulomas
-cavitation/bronchial damage less severe
How is latent Tb diagnosed?
-PPD (purified protein derivative)
How does a PPD work?
I.D. injection of tuberculin material which stimulates a delayed type hypersensitivity mediated by T cells (causes induration within 48-72 hrs)
What can cause a false positive PPD?
immunization with BCG or infection is a non-TB mycobacteria
How does an IGRA (Quantiferon gold Quan-TB, T-spot) work?
Patient blood cells are exposed to antigens from MTB and the amount of INF-y released is measured. (no false positive from BCG or NTM infections)
Latent Tb tests in HIV patients
False negatives can occur in both tests due to lack of immune response, called anergy
How is latent Tb treated?
INH for 9 months OR
INH and Rifapentine for 3 months
What determines a positive PPD?
What is a positive PPD in someone with no known risk factors?
What is a positive PPD in a homeless, IVDU, nursing home resident, recent immigrant, children under 4?
What is a positive PPD in a HIV, immunosuppressed, organ transplant, prior TB?
Do you measure the erythema or induration in a PPD?