Fentanyl and its metabolite, morphine, high levels of the morphine glucuronides, and hydromorphone were also detected. “All in all, this suggests they’re taking fentanyl and morphine,” Dr. Melanson said. “We might add a comment that says, ‘Suggestive of fentanyl and morphine use, prescriptions for which were not found in the medical record,’” and that those results could be from heroin use.
Drs. Melanson and Petrides plan to publish their findings on how well the clinicians are interpreting results once the study is complete.In the debate over oral fluid versus urine as the specimen of choice, Dr. Melanson referred to the laboratory’s study, which showed that amphetamines and the heroin metabolite 6-acetylmorphine were detected at higher rates in oral fluid. She also supported oral fluid for being noninvasive, less likely to be adulterated, more effective at detecting drugs in real time, and resisting poppy products and overhydration. Dr. Petrides noted the disadvantages of testing oral fluid: small specimen volume, dependence on collection device and person performing collection, and unknown windows of detection. The laboratory’s study showed that benzodiazepines, buprenorphine, and cocaine were detected better in urine compared with oral fluid, she said.
Drs. Melanson and Petrides reached a compromise by reviewing patient records to determine the performance of each matrix for prescribed medications. “For prescribed medications in the study—alprazolam, oxycodone, clonazepam, lorazepam, morphine, diazepam, and hydromorphone—the detection rates were higher in urine than oral fluid,” Dr. Petrides said, adding that it therefore may be better to use urine in a pain management setting but not in an addiction setting.
They looked more closely at the heroin metabolite 6-acetylmorphine, which gets metabolized to morphine. 6-AM was better detected in oral fluid, in accordance with its biochemical properties. Their data showed that morphine did not have a preference for the matrix in which it was detected.
“What we hypothesized was that where you would find the morphine is dependent on the time of collection in relation to the time of ingestion,” Dr. Petrides said.
Plotting the oral fluid-to-urine ratio of morphine concentration revealed a time course. In oral fluid, there is a bell-shaped curve. “When you see a low result in oral fluid, it can either be due to recent use or it can be due to remote use. It’s hard to say whether if you get a positive result for 6-AM in oral fluid exactly when the patient took it,” Dr. Petrides said. “So oral fluid is the preferred matrix for 6-AM and amphetamine. But using a ratio of oral fluid-to-urine morphine could assist with interpreting 6-AM results.”
The final proposed testing algorithm settled on oral fluid as the preferred matrix for 6-AM and amphetamines, and urine for 7-aminoclonazepam, lorazepam, oxazepam, hydromorphone, oxymorphone, buprenorphine, and cocaine. More studies are needed to determine the preferred matrix for fentanyl, tramadol, MDMA/MDA, and methadone.
Dr. Petrides closed the session on a note about continued challenges from clinicians. A 45-year-old woman with advanced cervical cancer was prescribed oxycodone for pelvic pain. When a urine toxicology panel (by LC-MS/MS) revealed the presence of benzoylecgonine, a cocaine metabolite, she denied using cocaine. The patient suggested to her physician that her oral fluid contact with her dog, which had been prescribed the antibiotic clindamycin, caused her urine to test positive for cocaine. The clinician requested a test for clindamycin for the patient.
“This was a real case,” Dr. Petrides said. “It was pretty interesting to try to convince the clinical team that this could not possibly ever happen.”
Amy Carpenter Aquino is CAP TODAY senior editor.