WORKING UP AN OLD POSITIVE PPD

A 40-year-old woman tested positive for purified protein derivative (PPD) six years ago. A chest x-ray at the time was negative. After completing the required course of isoniazid (INH), she has had negative chest x-rays for the past five years. Now, as she is preparing to enroll in college, her chest x-ray shows hilar adenopathy. The woman has no fever or cough, and she has experienced no change in weight. What workup would you do?
—Ellen Urrutia, MD, Morristown, N.J.

Biopsy is the best bet. It is reasonable to proceed with additional investigation and assume that her TB was treated adequately six years ago. Remember that INH reduces the lifetime risk of pulmonary TB from 10% to <1% (N Engl J Med. 2004;350:2060-2067). Chest CT would be useful for ascertaining if there is pathologic lymphadenopathy, and aggressive measures would be warranted if additional clues pointed toward a neoplastic process. More advanced imaging may not be helpful, as studies in Taiwan have shown that positron emission tomography scanning has not been able to differentiate neoplastic from infectious (i.e., mycobacterial) lymphadenopathy (Chest. 2003;124:893-901).
—Cedric W. Spak, MD, MPH (115-23)

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