Which of the following indicates a positive PPD test for a high-risk individual?

A positive PPD (purified protein derivative) test indicates exposure to the bacteria that cause tuberculosis (TB) and is interpreted based on the individual's risk factors for developing TB. For high-risk individuals, a 10mm induration is considered a positive result. This threshold recognizes that these individuals are more susceptible to TB infection and the potential complications that could arise from it.

The reason a 10mm induration is used as the cutoff for high-risk individuals is due to their increased likelihood of having a significant immune response to the TB antigens in the PPD test. This can include individuals with HIV, those who have had recent contact with someone who has TB, or those with underlying medical conditions that compromise their immune systems.

The thresholds for induration differ for various risk categories. For example, 15mm is typically considered the positive threshold for persons with no known risk factors. Similarly, a 5mm induration may indicate a positive test in immunocompromised individuals or those with close contact to someone with active TB. Hence, for a high-risk individual, the 10mm cut-off is the appropriate benchmark for a positive PPD response.