Tuberculosis

Aka: Tuberculosis, Mycobacterium tuberculosis, Tb

1. See Also
   1. Tuberculosis Screening in Children
2. Epidemiology
   1. Worldwide
      1. Latent Tuberculosis Prevalence: 2 Billion people
         1. One third of world population has latent Tuberculosis
         2. Over half of cases in China, India, and Southeast asia
      2. Active Tuberculosis will develop in 10% of latent cases
         1. Most frequent cause of death for young adults
         2. In 1998, 8 million active cases, 2 million deaths
   2. United States
      1. Incidence rose 74% between 1953 to 1985
      2. Active Tb Incidence has fallen to 13,779 cases in 2006 (4.6 cases per 1000,000)
         1. http://www.cdc.gov/tb/surv/surv2006/pdf/FullReport.pdf
      3. Latent Tb Incidence: 10-15 Million in U.S.
      4. Incidence in U.S. born patients declined since 1992
      5. Incidence in foreign born persons Incidence increasing (4-5x U.S)
         1. Latent TB infection in 30-50% of Minnesota refugees
         2. Drug-resistant TB is twice as likely in refugees
      6. Other factors related to resurgence of Tuberculosis in the United States
         1. HIV epidemic
         2. Multidrug-Resistant Tuberculosis
3. History
   1. George Orwell died of Tuberculosis in 1950
      1. Shortly after Nineteen Eighty four was published
4. Transmission
   1. Mycobacterium tuberculosis carried in airborne droplets
   2. Active Pulmonary or Laryngeal Tuberculosis transmitted
      1. Sneeze, cough, speak, or sing
5. Risk Factors
   1. Latent Tuberculosis
      1. See Tuberculosis Risk Factors
   2. Reactivation to active Tuberculosis Risk Factors
      1. Latent Tuberculosis acquired in last 2 years
      2. Immunocompromised patients (e.g. HIV, Cancer, immunosuppressants, TNF agents)
         1. HIV patients have a 10% annual risk of reactivation
      3. Children under age 4
      4. Substance use (esp. Illicit Drugs, but probably also Tobacco and Alcohol)
      5. Prior Tuberculosis with scarring on Chest XRay (apical fibronodular changes)
      6. Body weight >10% below Ideal Weight
      7. Chronic Kidney Disease (esp. End Stage Renal Disease)
      8. Diabetes Mellitus
      9. Prior Bariatric Surgery (Gastric Bypass surgery)
      10. Silicosis
6. Course
   1. Tuberculin Skin Test conversion within 2-10 weeks
   2. Latent Tuberculosis initially
      1. Tuberculin Skin Test positive without signs, symptoms
      2. Tubercle bacilli remain dormant and viable for years
   3. Lifetime risk of developing active TB: 10%
   4. Highest risk is greatest within 2 years of exposure (5% of latent cases become active)
      1. See risk factors above
7. Symptoms
   1. Presentation often mimics cancer presentation
   2. Non-specific presentation (most common)
      1. Fatigue
      2. Weight loss
      3. Cachexia
      4. Night Sweats
   3. Pulmonary Tuberculosis symptoms
      1. Productive cough (typically 2-3 weeks)
      2. Hemoptysis (uncommon)
      3. Pleuritic Chest Pain
      4. Dyspnea
8. Signs
   1. Sites of Involvement
      1. Primary infection: lung involvement
   2. Disseminated Disease
      1. See Extrapulmonary Tuberculosis
9. Diagnosis
   1. Tuberculin Skin Test (TST, Purified Protein Derivative, PPD)
   2. Mycobacterium Tuberculosis Antigen-Specific Interferon-Gamma Release Assay (IGRA)
      1. IGRA tests will likely replace the Tuberculin Skin Test
      2. Cost is approaching that of TST
   3. In suspected pulmonary Tuberculosis
      1. Induced Sputum samples on 3 consecutive days or
      2. Gastric aspirate may be used in young children or
      3. Bronchoscopy with bronchoalveolar lavage and biopsy
   4. Detection of organisms
      1. Acid fast stain (Sputum, body fluid, biopsy)
         1. Sensitive to >5000 bacilli per ml
      2. Fluorescent stains and DNA probes for rapid diagnosis
      3. Mycobacterial cultures
         1. Sensitive to 10 bacilli per ml
10. Labs
    1. HIV Test
       1. Test every person with Tuberculosis
11. Imaging: Chest XRay
    1. Pleural Effusion
    2. Hilar Adenopathy
    3. Cavitary lung lesion (higher risk for infectious spread to contagious contacts)
    4. Miliary lesions (disseminated spread throughout lung)
       1. Associated with capillary lesions
       2. Associated with immunocompromised conditions (e.g. AIDS)
    5. Upper lobe cavitary lesion or infiltrate
       1. Apical and posterior segments often affected
       2. Superior segment of lower lobes may also be affected
    6. Ghon Complex
       1. Healed primary peripheral lesion
       2. Calcified hilar node
    7. HIV positive Chest XRay correlates with CD4 Count
       1. CD4 Cell Count <200
          1. Mediastinal adenopathy
       2. CD4 Cell Count >200
          1. Upper lobe infiltrates and cavitation
    8. Findings not suggestive of prior Tb fibrotic lesion
       1. Isolated granuloma on Chest XRay
12. Management
    1. See Latent Tuberculosis Treatment
       1. Positive PPD without signs of active Tb
    2. See Active Tuberculosis Treatment
    3. Protocols for active Tuberculosis management
       1. Susceptible Tuberculosis Treatment
       2. Possibly Resistant Tuberculosis Treatment
       3. Multiple Drug Resistant Tuberculosis Treatment
13. Complications
    1. See Extrapulmonary Tuberculosis
14. Prevention
    1. Bacille Calmette-Guerin Vaccine (BCG vaccine)
       1. May be indicated in high risk young children in endemic areas
15. Resources
    1. See Tuberculosis Resources
16. References
    1. Frieden (2003) Lancet 362:887-99
    2. Potter (2005) Am Fam Physician 72:2225-35