An acute presentation of TB

In our #AMreport @WCHospital, we reviewed a case of active pulmonary tuberculosis. In our case, the patient presented with a two week history of a non-productive cough as the only symptom. A chest x-ray done revealed findings similar to attached image (figure 1: courtesy of wikipedia). The patient had sputum positive for acid fast bacilli and was treated with RIPE regimen.

1024px-miliary_tuberculosis_28747175683029
Miliary TB in this chest x-ray is noted with some hilar fullness. The more common presentation with active TB on chest x-ray is a notable right middle lobe collapse with hilar lymphadenopathy. Alternatively many mediastinal lymph nodes can be seen and are referred to as Ghon lesions. (courtesy wikipedia)

Learning points:

  1. What is TB?
  2. What is difference between active and latent TB?
  3. What is RIPE regimen?
  4. Risk factors for TB.

What is TB?

  • TB is caused by Mycobacterium tuberculosis (figure 2).
  • Transmission is primarily airborne by inhalation.
    • Lungs are primary focus of infection as a result.


What is the difference between active and latent TB?

800px-tb_in_sputum
Figure 2: M.tuberculosis stained in sputum (courtesy wikipedia)
  • Latent TB infection (LTBI)
    • Asymptomatic (i.e manifestations of the disease are contained by immune system)
    • Can be detected by tuberculin skin test (TST) or interferon-gamma release assay (IGRA)
      • false-positive results  can occur in patients who have previously received Bacillus Calmette–Guérin (BCG) vaccine after infancy and many times.
      • IGRA is a more specific test for the above-mentioned populations
  • Active TB infection
    • Symptomatic: fever, night sweats, cough, fatigue, weight loss for a period of >2 weeks (i.e manifestations of the disease are NOT contained by immune system).
    • TST and IGRA have no role in active TB.
      • Both test have poor sensitivity and specificity in active disease.
    • Patients should be isolated in negative pressure rooms if there is a strong suspicion of active TB.
    • Arrange for 3 morning sputum for AFB.
      • If 3 consecutive sputum samples are negative for AFB then the patient can be removed from isolation.

What is the RIPE regimen?

  •   RIPE regimen or also known as quadruple therapy consists of three bactericidal and one bacteriostatic agent.
  • Patients with active TB should received RIPE therapy until susceptibilty results are available.
  • Quick memory aid for the bactericidal  agents:
    • TB goes to the grave with RIP (Rifampin, Isoniazid, Pyrazinamide)
      8izn5prxt
    • Ethambutol is bacteriostatic agent with the main complication being optic neuritis
    • Rifampin has the main side effects of hepatotoxicity and produces orange appearing bodily fluids (eg. sweat, urine)
    • Isoniazid has the main complication of peripheral neuropathy and hepatoxicity.
      • Patients must supplemented with pyrodoxine (B6) 10-25 mg PO daily to decrease risk of neuropathy.
    • Pyrazinamide has side effects not limited to GI intolerance and liver injury.

Risk Factors for TB

16897-illustration-of-a-globe-pv~2 billion worldwide affected with TB.

  • Birth and residence in an endemic area
  • Institutionalized individuals (close contact dwelling)
  • Healthcare workers.
  • HIV, immunosuppression.
  • Chronic kidney disease, diabetes.
  • Alcohol abuse and smoking.

 

References:

  1. Canadian TB Standards 7th Edition 

-B

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