Recognizing and managing Tuberculosis on the USMLE Step 2 CK exam

by / Tuesday, 06 July 2010 / Published in Internal Medicine


  • 1° TB affects the lower lobes and is usually asymptomatic
  • It occurs in specific groups such as immigrants, HIV+ patients, homeless patients, and alcoholics.

Signs and Symptoms:

  • Night sweats
  • Fever
  • Cough
  • Sputum
  • Weight loss


  • CXR is the best initial diagnostic test
  • Do an acid-fast stain of the sputum to confirm diagnosis


  • Treatment with 4 anti-TB medications should be started with six months of therapy being the standard of care
  • Isoniazid (6 months), Rifampin (6 months), Pyrizinamide (2 months), and Ethambutol (2 months)
  • Do LFT’s because these medications can cause liver toxicity (stop all medications if transaminase levels reach 5x the upper limit of normal)

Specific Toxicities caused by TB drugs:

Isoniazid – peripheral neuropathy, add B6

Rifampin – red/orange colored body secretions

Pyrazinamide – hyperuricemia

Ethambutol – optic neuritis

The PPD test

A screening test for those in risk groups.

Testing criteria is as follows:

  • 5mm: close contacts, HIV+, steroid users
  • 10mm: for those who are in the “high-risk” groups mentioned above
  • 15mm: those with no increased risk

If PPD is positive, do the following:

  1. CXR
  2. If CXR is abnormal, do a sputum stain
  3. If sputum stain is positive, start 4-drug therapy

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