For high-risk populations, what is considered a positive result in a PPD test?

In high-risk populations, a positive result in a PPD (purified protein derivative) test is defined as an induration of 5 mm or more. This threshold is established because individuals in these groups, which include those with a known exposure to tuberculosis (TB), immunocompromised individuals (such as those with HIV), and close contacts of individuals with active TB, have a higher risk of developing the disease.

A 5 mm induration indicates enough of an immune response to show that the person has been infected with the Mycobacterium tuberculosis bacteria, which is critical for early detection and preventive treatment. Understanding the specific criteria for what constitutes a positive test in high-risk groups is essential for effective screening and management of tuberculosis, which remains a significant public health issue.