To the Editor.
—Discussions in JAMA have raised concerns about false-negative1 and false-positive2 results of urine drug screening. Exposure to a potentially common source of an innocently positive screening test for opiates has increased my awareness of these issues and suggested to me that information about this source should be disseminated.
Report of a Case.
—A 26-year-old woman presented to us in response to an advertisement seeking normal subjects for research. Her medical history was significant only for chemocautery of a cervical wart. She was receiving no medications and denied use of alcohol or other drugs. Findings on physical examination were normal. Routine blood tests were conducted and revealed no significant abnormalities. Preliminary urine drug screening was positive for opiates. Gas chromatography-mass spectroscopy confirmed the presence of morphine and codeine. The subject convincingly denied any known ingestion of opiates. Review of oral intake revealed that she had eaten