Commentary

Drug testing is an important component of pain management, and a growing laboratory industry. Simultaneous increases in the abuse of opioid medications and the numbers of patients seeking pain relief have necessitated drug monitoring in patients receiving pain medications. An additional factor contributing to the development of drug monitoring programs has been the increasing rate of opioid-related deaths involving prescribed opioids rather than heroin overdoses. Drug monitoring programs seek to demonstrate that patients are in compliance with currently prescribed medications, that they exhibit no evidence of using nonprescribed medications including illicit drugs, and that there is no evidence of diversion of scheduled opioids. Individuals in pain management treatment have been shown to have a higher rate of substance abuse than the general population, and some individuals receive multiple prescriptions from multiple physicians, sometimes selling these opioids to substance abusers.

This case study demonstrates the complexities of pain-management drug testing and the limitations of immunoassays to provide the needed information for proper interpretation of urine drug test results. As shown in this case, in-house urine immunoassays for 6-acetylmorphine and buprenorphine tested positive, and fentanyl results were invalid. These results caused the physician to consider illicit heroin abuse and use of the nonprescribed buprenorphine scheduled opioid, while providing no information on potential fentanyl use. All these misleading test results were caused by cross-reactivity of prescribed drugs or interference from a highly concentrated urine specimen. For these reasons, a chromatographic mass spectrometry confirmation test is almost always needed. In this case, the high urine morphine concentrations from prescribed morphine most likely triggered false-positive buprenorphine and 6-acetylmorphine immunoassay results, with a possible contribution of the patient's hydroxychloroquine medication, which also has been shown to generate false-positive buprenorphine results. The high urine creatinine concentration in this patient's urine also affected the ability of the fentanyl assay to yield valid immunoassay results. The case study documents the importance of laboratory professionals' knowledge and experience in informing the physician's interpretation of pain management urine test results.

• Received for publication June 3, 2014.
• Accepted for publication June 5, 2014.

• © 2014 American Association for Clinical Chemistry