At what point should a patient have repeat chest x-ray after reporting a prior (10 years ago) positive purified protein derivative (PPD) result with subsequent isoniazid therapy? The patient reports having a negative chest x-ray two years ago and is currently set to begin working in a hospital setting with possible TB exposure.
—TYSHA S. HOLMES, PA-C, Fort Jackson, S.C.

This patient’s PPD will remain positive even though he has been treated, and a repeat PPD should not be administered. Since his most recent chest x-ray was two years ago, I would recommend repeat imaging to serve as baseline before he starts work in a new hospital. Current Occupational Safety and Health Administration (OSHA) regulations do not require periodic chest x-rays for a health-care worker who is PPD-positive unless symptoms develop. Most institutions require PPD-positive employees to complete a questionnaire on the same schedule as PPDs are administered (every three months for high-risk settings, every six months for intermediate risk, and annually for low-risk settings). The questionnaire inquires as to presence of cough, weight loss, fatigue, and other symptoms suggestive of TB. While not required by OSHA, some institutions mandate a chest x-ray every two to three years in the PPD-positive employee.
—JoAnn Deasy, PA-C, MPH