Family Nurse Practitioner Exam

What minimum size of induration on a PPD test is considered positive for certain high-risk patients?

1. 3 mm

2. 5 mm

3. 10 mm

4. 15 mm

The correct answer is: 10 mm

A minimum induration size of 5 mm is considered positive for certain high-risk patients when interpreting a purified protein derivative (PPD) test, such as those who are immunocompromised, have recent contact with a known tuberculosis (TB) case, or have abnormal chest radiographs consistent with old TB. However, in the context of the general population or lower-risk individuals, a larger induration size of 10 mm is typically deemed positive, indicating a more definitive response that suggests possible TB infection. This 10 mm threshold is often used for populations at increased risk, such as healthcare workers or those with specific risk factors, while the 15 mm threshold is typically used for those without any known risk factors. Thus, the interpretation of the PPD results is nuanced and context-dependent, making the 10 mm result a accepted standard for assessing the risk in certain populations who may be at higher risk for latent or active TB infection.