What to do for a nurse with a PPD (Purified Protein Derivative) result of 12 mm?

Management of a Nurse with Positive PPD (12 mm)

Isoniazid for 6 months is the recommended treatment for this nurse with a 12 mm PPD result. 1, 2

Assessment and Interpretation

A PPD (Purified Protein Derivative) result of 12 mm in a healthcare worker (nurse) is considered positive and indicates latent tuberculosis infection (LTBI). For healthcare workers, a PPD reaction ≥10 mm is considered positive according to the American Thoracic Society and CDC guidelines 1.

The positive test requires:

• Clinical evaluation to rule out active TB
• Chest X-ray to exclude active pulmonary disease
• Consideration of treatment for LTBI

Treatment Algorithm

1. Rule out active TB:

   • Perform chest X-ray
   • Assess for symptoms (cough, fever, night sweats, weight loss)
   • If any suspicion of active TB, collect sputum samples for AFB smear and culture

2. If active TB is excluded (most likely scenario):

   • Proceed with LTBI treatment

3. Treatment options (in order of preference):

   • Isoniazid 300 mg daily for 6 months (preferred option) 1, 2
   • Alternative regimens:
     • Isoniazid 300 mg daily for 9 months (if higher risk factors present) 1
     • Rifampin 600 mg daily for 4 months (if isoniazid cannot be tolerated) 3
     • Once-weekly isoniazid-rifapentine for 12 weeks (3HP regimen) 3

Monitoring During Treatment

• Baseline liver function tests before starting treatment 1
• Monthly clinical evaluation for symptoms of hepatotoxicity (nausea, vomiting, abdominal pain, jaundice) 1, 3
• For patients >35 years old: monthly transaminase measurements 1
• Withhold isoniazid if:
  • Transaminase levels exceed 3× upper limit of normal with symptoms
  • Transaminase levels exceed 5× upper limit of normal if asymptomatic 1, 3
• Provide pyridoxine (vitamin B6) supplementation to prevent peripheral neuropathy 1

Rationale for Treatment

Healthcare workers are at increased occupational risk for TB exposure and infection. Treatment of LTBI significantly reduces the risk of progression to active TB, which would have serious implications for:

• The nurse's health (morbidity and mortality)
• Patient safety (risk of transmission)
• Workplace safety (exposure of colleagues)

Important Considerations

• Age of the nurse affects the risk-benefit ratio (hepatotoxicity risk increases with age) 1
• Treatment completion is critical for effectiveness 3
• Healthcare workers should be evaluated for preventive therapy regardless of age if they have a positive PPD 1
• The 6-month isoniazid regimen has been shown to be effective in preventing progression to active TB 4

Common Pitfalls to Avoid

1. Ignoring the positive result because the nurse is asymptomatic - this misses the opportunity to prevent active TB
2. Starting treatment without ruling out active TB - monotherapy is inadequate for active TB and can lead to drug resistance
3. Poor monitoring for adverse effects - hepatotoxicity can occur in approximately 17.6% of patients on isoniazid 5
4. Inadequate duration of therapy - incomplete treatment may not effectively prevent progression to active TB

By following this approach, you can effectively manage this nurse's latent TB infection while minimizing risks and ensuring optimal outcomes regarding morbidity, mortality, and quality of life.