What is the next step for a nurse practitioner with a 10mm soft, non-indurated reaction to a Mantoux (tuberculin skin test) and no symptoms of active tuberculosis (TB)?

From the Guidelines

The nurse practitioner with a 10mm soft, non-indurated reaction to a Mantoux test and no symptoms of active tuberculosis should be considered for treatment of latent tuberculosis infection (LTBI) because a 10mm induration is considered positive in individuals at increased risk of LTBI, such as healthcare workers 1. The interpretation of the tuberculin skin test (TST) is risk-stratified, and a reaction of ≥10 mm is considered positive for other persons at increased risk of LTBI, including those with medical risk factors that increase the probability of progression from LTBI to TB 1.

• Key points to consider in this scenario include:
  • The TST result is positive based on the 10mm induration, which is a significant reaction in individuals at increased risk of LTBI.
  • The absence of symptoms of active TB, such as fever, cough, or weight loss, suggests that the individual may have latent TB infection rather than active disease.
  • The recommended treatment regimens for LTBI include isoniazid 300mg daily for 6-9 months, with 9 months being preferred for optimal efficacy, or alternative regimens such as isoniazid plus rifapentine weekly for 12 weeks (3HP regimen) or rifampin 600mg daily for 4 months 1.
• Before starting treatment, it is essential to:
  • Obtain baseline liver function tests to monitor for potential hepatotoxicity associated with LTBI treatment.
  • Rule out active TB with a chest X-ray and symptom screening to ensure that the individual does not have active disease.
  • Provide monthly follow-up to monitor for medication side effects, particularly hepatotoxicity, and to ensure treatment adherence.
  • Prescribe pyridoxine (vitamin B6) 25-50mg daily with isoniazid to prevent peripheral neuropathy. Treatment of LTBI is crucial in healthcare workers because it significantly reduces the risk of progression to active TB disease, which can be life-threatening and highly contagious 1.

From the FDA Drug Label

Candidates for preventive therapy who have a tuberculin skin test reaction of 10 mm or more are also appropriate candidates for preventive therapy if they are a member of any of the following high-incidence groups Children who are less than 4 years old are candidates for isoniazid preventive therapy if they have > 10 mm induration from a PPD Mantoux tuberculin skin test persons under the age of 35 with a tuberculin skin test reaction of 10 mm or more are also appropriate candidates for preventive therapy

The reaction is 10mm and soft, but not indurated. The key term here is induration, which is the firm, raised tissue that is the actual measurement for a positive PPD test. Since the area is not indurated, the correct answer is C. The PPD is negative 2.

From the Research

Interpretation of Mantoux Test Results

The Mantoux test, also known as the tuberculin skin test (TST), is used to diagnose latent tuberculosis infection (LTBI). The test involves injecting a small amount of tuberculin into the skin, and the reaction is measured in millimeters of induration (swelling) after 48-72 hours.

Reaction Size and Interpretation

• A reaction size of 10mm or more is generally considered positive in individuals without any risk factors for TB 3.
• However, the presence of a red area without induration (swelling) is not typically considered a positive result.
• In this case, the nurse practitioner has a 10mm soft, non-indurated reaction to the Mantoux test, which may not be considered a positive result.

Next Steps

• Given the absence of symptoms of active tuberculosis (TB) and the non-indurated reaction, the next step would be to consider the result as negative or inconclusive.
• The Centers for Disease Control and Prevention (CDC) guidelines do not specify a repeat test in this scenario, but rather emphasize the importance of clinical judgment and consideration of individual risk factors.
• Therefore, the correct answer is:

Correct Answer

• C. The PPD is negative

Rationale

• The reaction size and characteristics do not meet the criteria for a positive result.
• There is no evidence to suggest that the nurse practitioner has active TB or requires immediate treatment.
• Further evaluation and testing may be necessary if symptoms develop or if there are concerns about exposure to TB.