An adolescent has a TB skin test prior to working as a volunteer in a hospital. The adolescent is healthy and has not travelled to or from a TB-endemic area or had close contact with anyone who has TB. The Mantoux skin test shows 10 mm of induration after 48 hours. What will the primary care pediatric nurse practitioner do?

• A. Ask the adolescent about exposure to homeless persons
• B. Order a chest radiograph to rule out active TB
• C. Reassure the adolescent that this is a negative screen
• D. Refer the adolescent to an infectious disease specialist

Answer: (C)

Interpreting tuberculin skin test results hinges on risk-based thresholds. In someone with no known TB risk factors, an induration of 15 mm or more is considered positive; smaller indurations are not. This adolescent has a 10 mm reaction but no recent contact with TB, no travel to endemic areas, and no other risk factors, so the result does not meet the threshold for a positive screen. Therefore no active TB workup is needed, and the appropriate action is to reassure that this is a negative screen. A chest radiograph is not indicated for a negative test in an asymptomatic, low-risk individual; referral to infectious disease is unnecessary in this scenario.