A tuberculin skin test induration of 5 mm or greater is considered positive in which individuals?

• A. Recent immigrants
• B. Immunocompromised or close contacts
• C. Healthcare workers
• D. People with no risk

Answer: (B)

Interpreting the tuberculin skin test depends on the person’s risk. A smaller induration can be considered positive in those at highest risk of progressing to active TB. A 5 mm or greater induration is positive for individuals who are immunocompromised or have had recent exposure to active TB (close contacts). This makes the option describing immunocompromised or close contacts the best fit. In other groups, the threshold is higher: recent immigrants and healthcare workers are typically evaluated with a 10 mm threshold, and people with no risk generally require around 15 mm. The key idea is that the size cutoff for a positive test varies with how likely someone is to have TB infection and to progress to disease.