A 3-year-old child had a PPD skin test 2 days ago. When the mother brings the child back to the clinic to have the nurse check the results, the nurse notes a 10 mm area of induration. This is considered
Rationale: In most healthy people with normal immune systems, an induration of 15 mm or greater is considered a positive reading. However, a 10 mm area of induration is considered positive for children under 4 years of age, IV drug users, travelers recently arrived from high-risk areas, and those exposed to mycobacterium at work. A negative skin test would have not induration or would have a small area (less than 5 mm in individuals who do not have a compromised immune system). TB tests must be read between 48 and 72 hours after taken for accurate results.