Interpretation of Urine Drug Screens: Metabolites and Impurities

A preliminary study of hydrocodone and hydromorphone to oxycodone ratios for distinguishing impurities from independent opioid use

BACKGROUND

Urine drug testing (UDT) monitors prescription compliance and/or drug abuse. However, interpretation of UDT results obtained by liquid chromatography-tandem mass spectrometry (LC-MS-MS) can be complicated by the presence of drug impurities that are detected by highly sensitive methods. Hydrocodone is a drug impurity that can be found as high as 1% in oxycodone pills.

OBJECTIVES

We evaluated the frequency and concentration of hydrocodone and its metabolite, hydromorphone, in patients taking oxycodone to check if the ratio of hydrocodone or hydromorphone to oxycodone could distinguish between oxycodone only use from those consuming additional opiates.

DESIGN & METHODS

We correlated LC-MS/MS results with medication records of 319 patients with positive oxycodone results over 7 months (4/2021-11/2021).

RESULTS

Fifteen of 319 patients with positive oxycodone results were taking oxycodone only. For these 15 patients, the mean ratio of hydrocodone to oxycodone was 0.57% (range 0.05%-3.35%), and the mean ratio of hydromorphone to oxycodone was 0.81% (range 0.18-3.51%).

CONCLUSIONS

Hydrocodone and/or hydromorphone are detectable in patients taking only oxycodone and can likely be identified as an impurity if their calculated ratio to oxycodone is <1 %. Further validation of the ratios in a larger sample size is recommended.

Impact of the Opioid Epidemic on Drug Testing

BACKGROUND

This review provides a description of how the opioid epidemic has impacted drug testing.

METHODS

Four major service areas of drug testing were considered, including emergency response, routine clinical care, routine forensics, and death investigations.

RESULTS

Several factors that the opioid epidemic has impacted in drug testing are discussed, including specimens, breadth of compounds recommended for testing, time to result required for specific applications, analytical approaches, interpretive support requirements, and examples of published practice guidelines.

CONCLUSIONS

Both clinical and forensic laboratories have adapted practices and developed new testing approaches to respond to the opioid epidemic. Such changes are likely to continue evolving in parallel with changes in both prescription and nonprescription opioid availability and use patterns, as well as emerging populations that are affected by the "waves" of the opioid epidemic.

Demand for Interpretation of a Urine Drug Testing Panel Reflects the Changing Landscape of Clinical Needs; Opportunities for the Laboratory to Provide Added Clinical Value

BACKGROUND

The direct detection of drugs and metabolites in urine using a targeted panel offers sensitive and specific detection in comparison to the traditional approach to urine drug testing (screen with reflex of samples with positive results to confirmation testing). The purpose of this study was to evaluate changes in clinical demand for the laboratory to provide interpretation of patient adherence and abstinence, based on reconciling laboratory results and individual patient medication information provided by the clinician. The shifts in toxicology testing likely reflect the inherent complexity of the data and associated interpretation.

METHODS

Retrospective testing results associated with a targeted urine drug panel and its related interpretation were collected from our laboratory. We examined the associated testing volume and positivity rates of each reported analyte over 5 consecutive years (2015-2019). Requests from clinicians for consultation regarding this test and use of interpretive comments for the most recent year (2019), as well as access to publicly available educational resources over two years (2018-2019) were collected.

RESULTS

The changes in test ordering patterns demonstrate shifting of clinical demands for toxicology testing, by increased adoption of a targeted panel for which laboratory-based interpretation is provided. Positivity rates reflect national shifts in controlled substance prescriptions. Several consultative services were accessed by clinicians suggesting interest and need.

CONCLUSION

The value of clinical urine drug testing is improved by providing laboratory-based result interpretation and consultative services.