Interpreting Tuberculin Skin Tests

In Episode 64 of Med School Question of the Week for USMLE, Faustine Ramirez, MedSchoolCoach expert tutor, answers this medical school question: A 22-year-old college graduate presents to the physician’s office to complete health clearance paperwork before starting her first job as a school teacher. She spent the summer volunteering daily at a homeless shelter and is excited to be starting her job in the fall. She has no past medical history and takes no medications. She was born overseas and moved to the United States when she was 2 months of age. She currently feels well and has no symptoms. Tuberculin skin testing at 48 hours reveals an induration of 12 mm. All previous tuberculin skin tests have been negative. Her last skin test was 6 months ago before starting her volunteer position. An x-ray of the chest shows no abnormalities. Which of the following is the most appropriate next step in management?

• Repeat tuberculin skin test in 6 weeks
• Repeat tuberculin skin test in 1 year
• Repeat chest x-ray
• Testing for underlying immunodeficiency
• Treatment with isoniazid for 9 months
• Treatment with rifampin, isoniazid, pyrazinamide, and ethambutol for 2 months
• No testing or therapy indicated