The Night-Shift Nurse with a Positive TB Skin Test
A 29-year-old registered nurse in a 200-bed community hospital reports a positive tuberculin skin test (12 mm induration) at her pre-employment screening. She was born in a country with high TB prevalence, received BCG as an infant, and has no symptoms. Her chest radiograph is normal. She is 14 weeks pregnant. The employee health record shows she has never had a prior TST or IGRA. The infection preventionist asks you whether she can start work on the medical-surgical unit tomorrow, and the nurse asks whether she needs treatment now. The hospital's policy says "positive TST = referral to physician" but gives no further guidance.
1. Interpret the test result and determine her work status.
Read the worked answer
Interpretation. A 12 mm induration is positive regardless of BCG history; BCG does not reliably cause reactions of this size, and prior BCG should not be used to dismiss a positive TST. Because she has no prior negative test, this represents newly identified latent TB infection rather than a documented conversion, but the clinical implication is the same: she needs evaluation for active disease and consideration of treatment for latent infection.
Work status. With a normal chest radiograph and no symptoms, she is not contagious and does not require exclusion from patient care. A symptom review and chest imaging have ruled out active pulmonary disease for practical purposes. She may work, including on the medical-surgical unit, while completing evaluation. If she developed symptoms, she would be removed from duty until active TB was excluded.
Documentation. Record the result, the symptom screen, the radiograph interpretation, and the decision in the employee health file. Do not record it as a conversion without a prior negative test.
2. Address her question about treatment during pregnancy and outline the follow-up plan.
Read the worked answer
Treatment discussion. Latent TB infection is treated to prevent progression to active disease. In pregnancy, the decision balances maternal benefit against fetal risk. Isoniazid with pyridoxine is generally considered the preferred option and can be started after the first trimester, though some guidance supports starting when the risk of progression is high. She should be referred to a physician or TB clinic for an individualized decision; the occupational health nurse does not prescribe but ensures the referral happens and the rationale is documented. She should be told that untreated latent infection carries a lifetime risk of reactivation, higher in the first two years after infection and with any later immunosuppression.
Follow-up plan. (1) Referral within two weeks to TB clinic or infectious disease. (2) Baseline liver function tests if treatment is started; symptom education for hepatotoxicity. (3) Pyridoxine to prevent peripheral neuropathy. (4) Symptom check at each visit; instruct her to report cough, fever, night sweats, or weight loss immediately. (5) Annual symptom screening while she remains untreated. (6) Update the policy to specify interpretation, referral pathway, and work restrictions. (7) Verify that the hospital's respiratory protection program and fit testing are current for her unit.