Clinical Case Study - Clinical Chemistry

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Urine drug testing in opioid therapy for chronic pain management. In: Kwong T, Magnani B, Rosano T, Shaw L, eds. The clinical toxicology laboratory: ...
Clinical Case Study However, the urine drug screen does have limitations. The majority of initial drug screens provided by most hospitals or clinics are immunoassays. Immunoassays are either drug specific (e.g., cocaine metabolites, cannabinoid metabolites) or class specific (e.g., amphetamines, benzodiazepines, opiates). Most immunoassays, in addition to being limited by the lack of specific drug identification, may also be confounded by either false-positive or falsenegative results. This case nicely demonstrates how cross-reactivity with nontargeted drugs and interfering substances can produce erroneous results. The use of more specific and sensitive analytical techniques such as tandem mass spectrometry will provide the specific identification of parent drugs/metabolites, as well as quantification. The ability to perform a quantitative analysis over a large concentration range (⬍100 to ⬎100000 ng/mL), offered by these more specific and sensitive methods, allows for the proper interpretation of complicated cases involving minor opiate metabolites. As demonstrated in this case, a good understanding of the metabolism of these opioids and the performance characteristics of the assays is critical for the correct interpretation of the results.

Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article. Authors’ Disclosures or Potential Conflicts of Interest: Upon manuscript submission, all authors completed the author disclosure form. Disclosures and/or potential conflicts of interest: Employment or Leadership: None declared. Consultant or Advisory Role: None declared. Stock Ownership: None declared. Honoraria: B.J. Magnani, Massachusetts Medical Society and Massachusetts Society of Addiction Medicine; and Albert Einstein College of Medicine. Research Funding: None declared. Expert Testimony: None declared. Patents: None declared.

References 1. Kwong T, Magnani BJ. Urine drug testing in opioid therapy for chronic pain management. In: Kwong T, Magnani B, Rosano T, Shaw L, eds. The clinical toxicology laboratory: contemporary practice in poisoning evaluation. 2nd ed. Washington (DC): AACC Press; 2013. p 447–58. 2. Hammett-Stabler C, Magnani BJ. Supporting the pain service. In: Magnani BJ, Bissell M, Kwong T, Wu A, eds. Clinical toxicology testing: a guide for laboratory professionals. Northfield (IL): CAP Press; 2012. p 15–26.

Commentary Marilyn A. Huestis*

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 opi-

National Institute on Drug Abuse, Baltimore, MD. * Address correspondence to the author at: National Institute on Drug Abuse, Biomedical Research Center, 251 Bayview Blvd., Suite 200, Rm. 05A-721, Baltimore, MD 21224. E-mail [email protected]. Received June 3, 2014; accepted June 5, 2014. DOI: 10.1373/clinchem.2014.224543 © 2014 American Association for Clinical Chemistry

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oids. 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

Clinical Case Study 6-acetylmorphine immunoassay results, with a possible contribution of the patient’s hydroxychloroquine medication, which also has been shown to generate falsepositive 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.

Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article. Authors’ Disclosures or Potential Conflicts of Interest: No authors declared any potential conflicts of interest.

Clinical Chemistry 60:12 (2014) 1485