TB note 11 4
- related: Tuberculosis
Spread
- mostly from cough/airdrop
- only 10 bacilli need to reach lung
- very rarely genitourinary
Pathogenesis
- phagocytosed by macrophage
- antigen produce cellular instead of B cell response, CD 4 and 8
- One of 2 outcomes
- Latent: infection contained not eliminated. Granulomas
- Active: not contained, spreads
Latent
- asymptomatic and not contagious
- 5% risk of reactivation first 1.5 years and then 5% risk lifetime reactivation
Active
- Sx of fever, night sweats, weight loss caused by TNF alpha immune response
- hemoptysis: cellular destruction and necrosis from immune response
- Advanced HIV pts can have nl CXR
- Other sx:
- could be any organ sx or part of body
- meningitis
- hepatitis
- spine, Pott's
- lymph
- pericardium
Latent TB Dx
- Asymptomatic tests if:
- from endemic and/or exposure
- health care worker
- immunocompromised condition, HIV
- TB skin test
- 5mm: HIV, organ transplant, immunocompromised
- 15mm: no risks
- Interferon gamma release assay: T cell response to TB ag in latent TB
- NIL: negative control, patient's blood not with any antigens, < 8 iu/ml. If higher then underlying inflammatory condition that causes false positive
- mitogen: positive control. Pt's blood with nonspecific activation of T cells, > 0.5. False negative can happen if < 0.5
- TB-NIL: TB antigen minus negative control
- Indeterminate: either negative or positive control failed. Test didn't work.
Active TB Dx
- Do not order IGRA or skin test.
- Sputum:
- 3 AFB smears, 8 hours apart: immediately. Infectious if positive, but only noninfectious if negative. Can still have TB
- non TB mycobacterium can stain positive
- nocardia can stain positive
- culture for M.TB
- NAAT DNA probe, PCR: can also look for rifampin, INH resistance
- 3 AFB smears, 8 hours apart: immediately. Infectious if positive, but only noninfectious if negative. Can still have TB
- CXR and CT
- high sensitivity for active TB
- low specificity 60-70%
- HIV pt can have unremarkable CXR
- Bronchoscopy:
- bronc x1 has lower sensitivity than sputum x3
- helpful if pt cannot produce sputum
Treatment
- Prior to treatment
- screen HIV
- CXR Latent:
- INH 9 months with B6
- rifampin 4 months: can have more drug drug interactions
- INH and rifapentin 3 months
- Follow monthly
- Ask about: nausea, anorexia, icterus, rash, paresthesia
- monitor ALT, AST, T bili (inh rifampin cause hepatitis)
- watchout out >3x upper limit of nl LFT
Active:
- RIPE: 4 drugs 2 months, and then 4 months INH/rifampin
- extend therapy if sputum clx positive after 2 months. Continue 7 months
- extrapulmonary: 9-12 months
MDR TB
- MDR if resistance to INH and rifampin
- extensively drug resistance: INH, R, fluoroquinolone, aminoglycoside