Accurate interpretation of drug test results is key to appropriate patient care in numerous settings including pain management. Despite recommendations that providers should consult laboratory professionals for guidance when necessary, literature demonstrating laboratorian expertise in drug test interpretation is lacking.


To evaluate participating laboratories’ performance on the case-based, interpretive (“dry”) challenge included with each Drug Monitoring for Pain Management proficiency testing program from 2012–2023.


All challenges (n = 23) required participants to identify if drug test results were consistent or inconsistent with prescribed medications in the case history. Relevant medications, presumptive and confirmatory drug test results, and participant responses were extracted from program summary reports and examined for performance and common themes.


Overall, 91.8% (6821 of 7431) of participant responses correctly identified whether drug testing was consistent with medications. There were 8 challenges with participant scores below 91.8% (range, 59.8% [49 of 82 responses] to 88.9% [193 of 217 responses]). Common knowledge gaps identified in these challenges included false-positive presumptive (screening) results, minor metabolism of opiates, and recognizing that presence of a nonprescribed drug is inconsistent with prescribed medications. Although some participants repeatedly responded incorrectly, there were no associations between laboratory type, personnel responding, or analytical performance with incorrect responses to interpretative challenges.


Program participants performed well overall, but several concerning educational gaps were identified. Laboratorians have a role in providing interpretative guidance for drug testing and should emphasize ongoing education to ensure competence in the setting of constantly changing prescribed and nonprescribed drug use.

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Competing Interests

The authors have no relevant financial interest in the products or companies described in this article.

Author notes

Portions of the data were presented at the International Association of Therapeutic Drug Monitoring and Clinical Toxicology annual meeting; September 26, 2023; Oslo, Norway.