Tuberculosis

Sep 16, 2019 admin HÔ HẤP, NHIỄM KHUẨN 0

Tuberculosis

Aka: Tuberculosis, Mycobacterium tuberculosis, Tb

II. Complications

  1. See Extrapulmonary Tuberculosis

III. Epidemiology

  1. Worldwide
    1. Latent TuberculosisPrevalence: 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 Tb cases, 2 million deaths
      3. In 2015, 10.4 million Active Tb cases, 1.4 million deaths
        1. An additional 0.4 million deaths occurred in HIV patients with Active Tb
  2. United States
    1. Latent TbIncidence: 10-15 Million in U.S.
    2. Active TbIncidence has fallen
      1. 2014 cases: 9,421 (2.96 per 100,000)
      2. 2006 cases: 13,779 (4.6 cases per 100,000)
      3. 1992 cases: 26,673 (10.5 cases per 100,000)
    3. Active TbIncidence in U.S. born patients declined since 1992
      1. Incidence rose 74% between 1953 to 1985, before it started falling in 1992
    4. Active TbIncidence in foreign born persons Incidence increasing (4-5x U.S)
      1. Foreign borne patients represent 66% of new Tb cases in U.S.
      2. Foreign borne patient Active TbIncidence: 15.4 cases per 100,000
      3. U.S. borne patient Active TbIncidence: 1.2 cases per 100,000
      4. Latent Tb infection in 30-50% of Minnesota Refugees
      5. Drug-resistant TB is twice as likely in Refugees
    5. Active TbIncidence by ethnic groups in the United States (in 2014)
      1. Asians: 17.8 cases per 100,000
      2. Native hawaiians and others from the pacific islands: 16.9 per 100,000
      3. American indians or alaskan natives: 5.0 per 100,000
      4. Blacks: 5.1 per 100,000
      5. Hispanics: 5.0 per 100,000
      6. Whites: 0.6 per 100,000
    6. Other factors related to resurgence of Tuberculosis in the United States
      1. HIV epidemic
      2. Multidrug-Resistant Tuberculosis
    7. References
      1. (2014) CDC – Trends in Tuberculosis, accessed online 11/2/2016
        1. http://www.cdc.gov/tb/publications/factsheets/statistics/tbtrends.htm

IV. History

  1. George Orwell died of Tuberculosis in 1950
    1. Shortly after Nineteen Eighty four was published

V. Transmission

  1. Mycobacterium tuberculosis carried in airborne droplets
  2. Active Pulmonary or Laryngeal Tuberculosis transmitted
    1. Sneeze, cough, speak, or sing

VI. Risk Factors

  1. Latent Tuberculosis
    1. See Tuberculosis Risk Factors (Tuberculosis Screening Indications)
  2. Reactivation to active Tuberculosis Risk Factors
    1. See Tuberculosis Risk Factors for progression from Latent to Active Disease (Latent Tb treatment indications)

VII. Course

  1. Tuberculin Skin Test conversion within 2-10 weeks of exposure
  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 (5-10% of latent cases become active)
    1. See Tuberculosis Risk Factors for progression from Latent to Active Disease (Latent Tb treatment indications)

VIII. Symptoms

  1. Latent Tuberculosis is asymptomatic
  2. Active Tuberculosis mimics other conditions
    1. May mimic cancer presentation (Night Sweats, weight loss)
    2. May mimic Community Acquired Pneumonia (cough, fever, mild Chest XRay infiltrate)
    3. Exercise a low index of suspicion for testing
  3. Non-specific presentation (most common)
    1. Fatigue
    2. Weight loss
    3. Cachexia
    4. Night Sweats
  4. Pulmonary Tuberculosis symptoms
    1. Productive cough (typically 2-3 weeks)
    2. Hemoptysis (uncommon)
    3. Pleuritic Chest Pain
    4. Dyspnea

IX. Signs

  1. Sites of Involvement
    1. Primary infection: lung involvement
  2. Disseminated Disease
    1. See Extrapulmonary Tuberculosis
  3. Findings to consider Tuberculosis Testing (e.g. undifferentiated cough in the emergency department)
    1. Mild Sinus Tachycardia
    2. Mild Hypoxia
    3. Tachypnea
    4. Low grade fever

X. Diagnosis

  1. Tuberculosis Screening
    1. See Tuberculosis Risk Factors (Tuberculosis Screening Indications)
    2. See Tuberculosis Screening for lab selection
    3. Tuberculin Skin Test (TST, Purified Protein Derivative, PPD)
    4. Mycobacterium Tuberculosis Antigen-Specific Interferon-Gamma Release Assay (IGRA)
      1. IGRA tests will likely replace the Tuberculin Skin Test in longterm
        1. Some caveats (e.g. age under 5 years old)
      2. Cost of IGRA is approaching that of Tuberculin Skin Test
  2. 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
  3. 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

XI. Labs

  1. Diagnostic testing as above
  2. HIV Test
    1. Test every person with Tuberculosis

XII. Imaging: Chest XRay

  1. See Tuberculosis Related Chest XRay Changes

XIII. Management

  1. Latent Tuberculosis
    1. See Latent Tuberculosis Treatment
    2. Positive PPD or IGRA without signs of Active Tb
      1. Confirm no Active Tb (cough, Night Sweats) before starting single drug Latent Tb management
      2. Chest XRay is performed at time of Latent Tb diagnosis
    3. Treatment indicated if risk of Tb Progression from latent to active disease
      1. See Tuberculosis Risk Factors for progression from Latent to Active Disease
  2. Active Tuberculosis
    1. See Active Tuberculosis Treatment
    2. Symptomatic patient (e.g. fever, weight loss, Hemoptysis)
      1. Patient isolated in negative pressure room and wears mask
      2. Healthcare workers wear N-95 Mask
      3. Obtain diagnostic testing
        1. Chest XRay
        2. Sputum acid-fast bacilli smear and culture
      4. Consult with pulmonology or infectious disease
      5. Consult public health
    3. Protocols for Active Tuberculosis management
      1. Susceptible Tuberculosis Treatment
      2. Possibly Resistant Tuberculosis Treatment
      3. Multiple Drug Resistant Tuberculosis Treatment
  3. Post-exposure Prophylaxis
    1. Indications
      1. Exposure to untreated active pulmonary or laryngeal Tuberculosis
      2. Regardless of prior BCG vaccine or prior Tuberculosis treatment
    2. Protocol: Asymptomatic contact
      1. Treatment indications based on Tuberculosis Testing at baseline AND 8-12 weeks after exposure
        1. Tuberculin Skin Test (PPD) of 5mm or greater OR
        2. Mycobacterium Tuberculosis Antigen-Specific Interferon-Gamma Release Assay positive
      2. Start treatment if positive testing
        1. Isoniazid (INH) with Vitamin B6 supplementation for 9 months
    3. Protocol: Symptomatic contact
      1. Follow Active Tuberculosis protocol as above

XIV. Complications

  1. See Extrapulmonary Tuberculosis

XV. Prevention

  1. Bacille Calmette-Guerin Vaccine (BCG vaccine)
    1. May be indicated in high risk young children in endemic areas

XVI. Resources

  1. See Tuberculosis Resources

XVII. References

  1. Orman, Moran and Swaminathan in Herbert (2016) EM:Rap 16(11): 2-3
  2. Frieden (2003) Lancet 362:887-99 [PubMed]
  3. Hartman-Adams (2014) Am Fam Physician 89(11): 889-96 [PubMed]
  4. Potter (2005) Am Fam Physician 72:2225-35 [PubMed]

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