Family Nurse Practitioner Exam

What is the minimum size of induration that is considered positive for recent exposure to tuberculosis?

1. 3 mm

2. 5 mm

3. 10 mm

4. 15 mm

The correct answer is: 5 mm

A positive tuberculin skin test (TST) indicates likely exposure to tuberculosis (TB) based on the size of the induration, measured in millimeters. For individuals with certain risk factors, including recent exposure to an infected individual, a minimum induration of 5 mm is considered positive. This threshold reflects the heightened risk in specific groups, such as those with HIV, recent contacts of TB cases, or those who have received organ transplants. In contrast, the other sizes for induration are interpreted based on different contexts. For example, a 10 mm induration is typically the cutoff for individuals who may be at increased risk, like healthcare workers or people with chronic conditions, while 15 mm is generally used for those with no known risk factors. The criteria aim to ensure accurate screening and subsequent action for at-risk populations, emphasizing the importance of the 5 mm standard for recent TB exposure.