What are some risk factors for TB exposure in the US?
Homelessness Crowded living conditions (prisons) Emigration/Travel from developing nations Health professionals Contact with TB pts
What are some risk factors for active/reactivation TB?
Immunosuppression (HIV) EtOH Preexisting lung dz DM Advancing age
What is the presentation of TB?
Cough/Hemoptysis Dyspnea Weight loss/Cachexia Fatigue Night sweats Fever (fever of unknown origin) Lymphadenopathy Prolonged symptoms > 3 weeks Extrapulmonary involvement
How do you dx active TB?
How do you dx latent TB (LTBI)?
Active: Sputum/blood/tissue culture (gold std but takes weeks) Sputum acid fast stain (rapid but lacks sensitivity) CXR w cavitary infiltrate in upper lobe (HIV pt may have lower lobe infiltrates +/- cavitation) Multiple fine nodular densities suggests Miliary TB
Latent: PPD (all +PPDs -> f/u CXR)
What is the relationship between the BCG vaccine and PPD?
BCG vaccination -> +PPD but does not preclude prophylaxis as recommended for unvaccinated pts (possible false positive PPD)
How do you read a PPD?
PPD injected intradermally on volar surface of forearm and then the diameter of the induration is measured at 48-72 hours. PPD is positive if:
> 5 mm: HIV, risk factors, TB contacts, CXR e/o TB > 10 mm: health care workers, homeless, IVDU, prison, resident of developing nation > 15 mm: no risk factors + everyone not above
Anergy = Immunosuppression, elderly, malnutrition may give false -PPD thus TB not ruled out
What type of hypersensitivity reaction is a PPD test?
Type IV Hypersentivity Reaction
Delayed (cell-mediated) type Sensitized T lymphocytes encounter antigen -> release lymphokines
What is the tx for TB?
All cases (active/latent) must be reported to health department.
Respiratory isolation if active TB suspected.
Active: Directly observed 4-drug therapy RIPE (Rifampin, INH, Pyrazinamide, Ethambutol) + vitamin B6 (pyridoxine) x 2 mo -> INH, Rifampin + vitamin B6 (pyridoxine) x 4 mo
Latent (+PPD w/o e/o active dz): INH + vitamin B6 (pyridoxine) x 6-9 mo or Rifampin x 4 mo