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
• 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