A 40-year-old woman with a history of polysubstance use presented to a methadone clinic with opioid use disorder and housing instability. The patient, who reported injecting intermittent cocaine and 2 to 3 g of what she believed to be fentanyl per day, was initiated on methadone therapy. Results of a urine drug screen (UDS) on her presentation day were positive for fentanyls and confirmed by liquid chromatography–mass spectrometry (parent fentanyl = 20.0 ng/mL, metabolite norfentanyl = 337.0 ng/mL). On day 23, results of her UDS and confirmatory testing were again positive for fentanyls, although no parent fentanyl was detected on confirmation, and the norfentanyl metabolite concentration (0.7 ng/mL) was barely above the detection threshold (0.5 ng/mL). This result was misinterpreted as the patient having relapsed, and she was discharged from clinic-associated housing despite her disavowal of new fentanyl use. Results of UDS on days 30 and 45 were negative for fentanyls. The patient struggled to maintain sobriety owing to her housing instability and subsequently relapsed, testing positive for fentanyls by UDS on day 51.
Weiss ST, Chinn M, Veach L. Reconsidering Reliance on Confirmatory Drug Testing in a Patient With Repeated Positive Urine Drug Screen Results: A Teachable Moment. JAMA Intern Med. 2021;181(12):1637–1638. doi:10.1001/jamainternmed.2021.6215
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