Q&A column

Editor: Frederick L. Kiechle, MD, PhD

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Q. What can laboratories expect to see after a medication such as Narcan is given for an opioid overdose?

A. November 2020—Narcan is a trade name for naloxone, a reversing agent for opioids that acts on the mu opioid receptor. Most hospital laboratories would not detect naloxone unless they were running sensitive LC-TOF-MS–based or LC-MS/MS–based screening methods that include it in their target compound database. GC-MS–based drug screening methods may not detect naloxone unless it is part of a targeted opiate assay.

If a sufficient amount of naloxone is present, it sometimes can produce a positive result in opioid immunoassay screening methods for such opiates as codeine and morphine or such opioids as oxycodone, oxymorphone, hydrocodone, and hydromorphone. Naloxone has very low cross-reactivity in opioid immunoassay screening methods—usually less than one percent—and will not typically give a positive response. Cross-reactivity in the fentanyl immunoassay kits is even lower or absent.

Even with low cross-reactivity, whether naloxone elicits a positive immunoassay response depends on the amount administered, route of administration, and timing of the dose relative to urine collection. If the dose is high or repeated, a positive immunoassay response due to naloxone is more likely. If urine is collected too soon after naloxone administration, insufficient drug will reach the urine to cause a positive mass spectrometry or immunoassay response. But too long a time between naloxone administration and urine collection will also lessen the chances of detection due to metabolism and clearance from the body. For example, detection of naloxone after a single intramuscular dose is far less likely than if naloxone is administered intravenously in repeated doses to counter a serious opioid overdose.

Jenkins AJ, Poirier JG III, Juhascik MP. Cross-reactivity of naloxone with oxycodone immunoassays: implications for individuals taking Suboxone. Clin Chem. 2009;55(7):1434–1436.

Straseski JA, Stolbach A, Clarke W. Opiate-positive immunoassay screen in a pediatric patient. Clin Chem. 2010;56(8):1220–1223.

Graham R. Jones, PhD
Member, CAP Toxicology Committee

Michael A. Graham, MD
Vice Chair, CAP Toxicology Committee

Q. There are conflicting views among my colleagues regarding the meaning of initial competency assessment. Some think that using a training checklist for new staff counts as the initial competency assessment because we are signing off that the staff are competent to perform patient testing and report results. Others believe an initial competency assessment is done shortly after training is completed, followed by the mid-cycle/six-month competency assessment and annual competency assessment. Please clarify.

A. Your inquiry regarding training and competency is addressed in two checklist requirements: GEN.55450 “Personnel Training” and GEN.55500 “Competency Assessment–Nonwaived Testing.”