An estimated 20 million patients in the United States have a substance use disorder (SUD), with hundreds of millions of prescriptions for controlled substances written annually. Consequently, urine drug screening (UDS) has become widely utilized to evaluate and treat patients with an SUD or on chronic opioid or benzodiazepine therapy.1
Used appropriately, UDS can be a valuable tool; there is ample evidence, however, that it has been misused, by some physicians, to stigmatize patients who use drugs of abuse,2 profile patients racially,2 profit from excessive testing,3 and inappropriately discontinue treatment.4
A patient-centered approach. We have extensive clinical experience in the use and interpretation of urine toxicology, serving as clinical leads in busy family medicine residency practices that care for patients with SUDs, and are often consulted regarding patients on chronic opioid or benzodiazepine therapy. We have encountered countless situations in which the correct interpretation of UDS is critical to providing care.
Over time, and after considerable trial and error, we developed the patient-centered approach to urine toxicology described in this article. We believe that the medical evidence strongly supports our approach to the appropriate use and interpretation of urine toxicology in clinical practice. Our review here is intended as a resource when you consider implementing a UDS protocol or are struggling with the management of unexpected results.
Urine toxicology for therapeutic drug monitoring
Prescribing a controlled substance carries inherent risks, including diversion, nonmedical use, and development of an SUD. Prescribed medications, particularly opioids and benzodiazepines, have been linked to a large increase in overdose deaths over the past decade.5 Several strategies have been investigated to mitigate risk (see “How frequently should a patient be tested?,” later in the article).
Clinical judgment—ie, when a physician orders a drug test upon suspecting that a patient is diverting a prescribed drug or has developed an SUD—has been shown to be highly inaccurate. Implicit racial bias might affect the physician’s judgment, leading to changes in testing and test interpretation. For example, Black patients were found to be 10% more likely to have drug screening ordered while being treated with long-term opioid therapy and 2 to 3 times more likely to have their medication discontinued as a result of a marijuana- or cocaine-positive test.2
Other studies have shown that testing patients for “bad behavior,” so to speak—reporting a prescription lost or stolen, consuming more than the prescribed dosage, visiting the office without an appointment, having multiple drug intolerances and allergies, and making frequent telephone calls to the practice—is ineffective.6 Patients with these behaviors were slightly more likely to unexpectedly test positive, or negative, on their UDS; however, many patients without suspect behavior also were found to have abnormal toxicology results.6 Data do not support therapeutic drug monitoring only of patients selected on the basis of aberrant behavior.6
Continue to: Questions and concerns about urine drug screening