Q&A column

Editor: Frederick L. Kiechle, MD, PhD

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Q. Are there any FDA-approved labor­atory-developed assays or point-of-care assays for detecting the presence of oxycodone or fentanyl in urine or blood?

A. There are two FDA-cleared instrument-based fentanyl assays for use with human urine: Fentanyl Urine Sefria Drug Screening Kit (Immunalysis) and Ark Fentanyl Assay (Ark Diagnostics).^1,2 Both assays have a cutoff concentration of 1.0 ng/mL of fentanyl but have minimal reactivity with the metabolite norfentanyl. The Thermo Scientific DRI Fentanyl Assay is not FDA cleared and has a cutoff of 2.0 ng/mL of fentanyl.

As with any immunoassay-based test, users should carefully review assay package inserts for immunospecificity for possible interfering substances that give false-positive results. Equally important is how well the assays can detect fentanyl analogs, such as acetylfentanyl, aryl­fentanyl, and butyrfentanyl, that have been reported to be present in street drugs. Since many definitive tests for fentanyl have been developed only for fentanyl and norfentanyl, a positive fentanyl immunoassay due to the presence of a fentanyl analog may not be confirmed by the definitive test. A study comparing the three immunoassays was published in 2018.³

FDA-cleared, instrument-based urine oxycodone test kits are available from Abbott Diagnostics, Beckman Coulter, Immunalysis, Ortho Clinical Diagnostics, Roche Diagnostics, Siemens Healthineers, and Thermo Fisher Scientific. Users should review cross-reactivities of the oxycodone metabolites noroxycodone, oxymorphone, and noroxymorphone since it is possible to have low oxycodone concentrations but much higher metabolite concentrations. Good reactivity for noroxycodone and oxymorphone is useful because the mean detection times for these two oxycodone metabolites are significantly longer than that for oxycodone.⁴

FDA-cleared point-of-care devices for urine fentanyl or oxycodone testing are available from MedTox Diagnostics and Abbott (Alere), among others. Because these are immunoassays, the issues discussed here for instrument-based assays also apply.