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Interpretation of Urine Drug ScreensMetabolites and Impurities

Educational Objective
Based on this clinical scenario and the accompanying image, understand how to arrive at a correct diagnosis.
1 Credit CME

A 50-year-old woman with chronic pain and recurrent infections from common variable immunodeficiency presented to a new primary care physician for management of her pain medications. Her pain was related to multiple vertebral fractures due to chronic steroid use for an inflammatory polyarthritis that was not responsive to hydroxychloriquine and methotrexate. Her pain medication regimen (methadone, 20 mg [3×/d]; immediate-release morphine, 30 mg [5×/d]; gabapentin, 1200 mg [2×/d]; duloxetine, 60 mg/d; and celecoxib, 200 mg [2×/d]) helped her independently complete instrumental activities of daily living. She reported no adverse effects (eg, somnolence or constipation). A comprehensive urine drug screen using immunoassay and mass spectrometry was ordered (Table 1).

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A. The patient is taking methadone and morphine.

With the increasing opioid dependence epidemic, clinicians must monitor the use of prescription opioids to identify misuse, addiction, and diversion (ie, selling or distributing prescribed medications). Urine drug screens can confirm whether patients on chronic opioids are using prescribed drugs and abstaining from illicit substances. Occasionally, it can be difficult to interpret a result as normal or abnormal based on the metabolites found in the urine.

Mass spectrometry–based methods of detection can identify and quantify multiple drugs and metabolites simultaneously. Additionally, mass spectrometry can measure very low concentrations of excreted drugs and detect minor metabolites and impurities not quantifiable with immunoassays. Medicare midpoint reimbursements for mass spectrometry–based tests range from $158.98 to $343.07, depending on the number of drug classes being tested.1

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Article Information

Corresponding Author: Geeta Nagpal, MD, Department of Anesthesiology, Northwestern University, Feinberg School of Medicine, 251 E Huron, F5-704, Chicago, IL 60611 (gnagpal@nm.org).

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Heiman reports serving as a member of the American Board of Internal Medicine test writing committee. No other disclosures were reported.

Additional Contribution: We thank the patient for sharing her experience and for granting permission to publish it.

References
1.
Centers for Medicare & Medicaid Services.  Clinical laboratory fee schedule. http://www.cms.gov/Medicare/Medicare-Fee-for-Service-Payment/ClinicalLabFeeSched/. Accessed February 20, 2017.
2.
Tenore  PL.  Advanced urine toxicology testing.  J Addict Dis. 2010;29(4):436-448.PubMedGoogle ScholarCrossref
3.
Phan  HM, Yoshizuka  K, Murry  DJ, Perry  PJ.  Drug testing in the workplace.  Pharmacotherapy. 2012;32(7):649-656.PubMedGoogle ScholarCrossref
4.
West  R, Crews  B, Mikel  C,  et al.  Anomalous observations of codeine in patients on morphine.  Ther Drug Monit. 2009;31(6):776-778.PubMedGoogle ScholarCrossref
5.
Washington State Agency Medical Directors’ Group.  Interagency guideline on prescribing opioids for pain. http://www.agencymeddirectors.wa.gov/Files/2015AMDGOpioidGuideline.pdf. Accessed April 25, 2017.
6.
West  R, West  C, Crews  B,  et al.  Anomalous observations of hydrocodone in patients on oxycodone.  Clin Chim Acta. 2011;412(1-2):29-32.PubMedGoogle ScholarCrossref
7.
Cone  EJ, Heit  HA, Caplan  YH, Gourlay  D.  Evidence of morphine metabolism to hydromorphone in pain patients chronically treated with morphine.  J Anal Toxicol. 2006;30(1):1-5.PubMedGoogle ScholarCrossref
8.
National Academy of Clinical Biochemistry.  Laboratory medicine practice guidelines: using clinical laboratory tests to monitor drug therapy in pain management patients. https://www.aacc.org/~/media/practice-guidelines/pain-management/rough-draft-pain-management-lmpg-v6aacc.pdf. Accessed June 7, 2017.
9.
Washington State Department of Labor and Industries.  Sample opioid treatment agreement. http://www.lni.wa.gov/ClaimsIns/Files/OMD/agreement.pdf. Accessed July 10, 2017.
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