Introduction
Urine drug testing has been the standard for monitoring opioid compliance in chronic pain patients. The COVID-19 pandemic created a dilemma for opioid monitoring by severely limiting in-person testing due to safety concerns. Oral fluid toxicology emerged as a feasible, alternative test due to its ability for remote sample collection under virtual supervision while minimizing infringements on patient privacy. However, the efficacy of these two tests for reliably detecting opioids should be explored prior to transitioning to testing only with oral fluids.
Methods
In this study, we compared morphine levels in oral fluid and urine toxicology studies from 5 randomly selected patients from a Chronic Pain Center who were regularly taking high doses (≥90 mEq) of extended-release morphine. Charts from the start of the COVID-19 pandemic until July 2022 were reviewed for urine and oral fluid testing results and medication regimens. All oral fluid and urine test results and collection methods were validated by a nationally recognized toxicology lab. Prescription Monitoring Program (PMP) reports were reviewed for each patient to observe pre-testing prescription trends.
Results
We found that the overwhelming majority of patients had at least 1 false negative oral fluid test result. The remainder of the oral fluid results were below threshold (10 ng/mL) or ranged from 11.3 to 54 ng/mL of morphine. 80% of patients (n = 5) had at least one negative or positive-but-below-threshold (10 ng/mL) result in their oral fluid sample analyses. In contrast, none of the urine studies had negative results. Urine studies for all patients were positive for morphine and well-above primary cutoff values (100 ng/mL) with levels >6000 ng/mL. PMP reports did not reveal any aberrant drug taking behavior in any of the patients. No unprescribed medications or illicit substances were detected in any of the oral or urine samples.
Conclusion
The prevalence of false negative results for the detection of morphine metabolites in oral fluid toxicology may be higher than clinicians are currently aware of. Physicians and other providers monitoring opioid compliance in chronic pain patients should keep this possibility in mind when selecting toxicology tests and making conclusions about aberrant drug-taking behavior. Larger scale studies are needed to compare oral fluid and urine levels of morphine with extension to other commonly prescribed opioids.
Disclosure
Evan Chung, MD: None, Joseph Valenza, MD: None