Urine drug tests (UDTs) are useful clinical tools for assessing and monitoring the risk of misuse, abuse, and diversion when prescribing controlled substances, or for monitoring abstinence in patients with substance use disorders (SUDs). However, UDTs have been underutilized, and have been used without systematic documentation of reasons and results.1,2 In addition, many clinicians may lack the knowledge needed to effectively interpret test results.3,4 Although the reported use of UDTs is much higher among clinicians who are members of American Society of Addiction Medicine (ASAM), there is still a need for improved education.5
The appropriate use of UDTs strengthens the therapeutic relationship and promotes healthy behaviors and patients’ recovery. On the other hand, incorrect interpretation of test results may lead to missing potential aberrant behaviors, or inappropriate consequences for patients, such as discontinuing necessary medications or discharging them from care secondary to a perceived violation of a treatment contract due to unexpected positive or negative drug screening results.6 In this article, we review the basic concepts of UDTs and provide an algorithm to determine when to order these tests, how to interpret the results, and how to modify treatment accordingly.
Urine drug tests 101
Urine drug tests include rapid urine drug screening (UDS) and confirmatory tests. Urine drug screenings are usually based on various types of immunoassays. They are fast, sensitive, and cost-effective. Because immunoassays are antibody-mediated, they have significant false-positive and false-negative rates due to cross-reactivity and sensitivity of antibodies.7 For example, antibodies used in immunoassays to detect opioids are essentially morphine antibodies, and are not able to detect semisynthetic opioids or synthetic opioids (except hydrocodone).7 However, immunoassays specifically developed to detect oxycodone, buprenorphine, fentanyl, and methadone are available. On the other hand, antibodies can cross-react with molecules unrelated to proto-medicines or drug metabolites, but with similar antigenic determinants. For example, amphetamine immunoassays have high false-positive rates with many different classes of medications or substances.7
Urine drug tests based on mass spectrometry, gas chromatography/mass spectrometry (GC/MS), and liquid chromatography/mass spectrometry (LC/MS) are gold standards to confirm toxicology results. They are highly sensitive and specific, with accurate quantitative measurement. However, they are more expensive than UDS and usually need to be sent to a laboratory with capacity to perform GC/MS or LC/MS, with a turnaround time of up to 1 week.8 In clinical practice, we usually start with UDS tests and order confirmatory tests when needed.
When to order UDTs in outpatient psychiatry
On December 12, 2013, the ASAM released a white paper that suggests the use of drug testing as a primary prevention, diagnostic, and monitoring tool in the management of addiction or drug misuse and its application in a wide variety of medical settings.9 Many clinicians use treatment contracts when prescribing controlled substances as a part of a risk-mitigation strategy, and these contracts often include the use of UDTs. Urine drug tests provide objective evidence to support or negate self-report, because many people may underreport their use.10 The literature has shown significant “abnormal” urine test results, ranging from 9% to 53%, in patients receiving chronic opioid therapy.2,11
The CDC and the American Academy of Pain Medicine recommend UDS before initiating any controlled substance for pain therapy.12,13 They also suggest random drug testing at least once or twice a year for low-risk patients, and more frequent screening for high-risk patients, such as those with a history of addiction.12,13 For example, for patients with opioid use disorder who participate in a methadone program, weekly UDTs are mandated for the first 90 days, and at least 8 UDTs a year are required after that.
However, UDTs carry significant stigma due to their association with SUDs. Talking with patients from the start of treatment helps to reduce this stigma, and makes it easier to have further discussions when patients have unexpected results during treatment. For example, clinicians can explain to patients that monitoring UDTs when prescribing controlled substances is similar to monitoring thyroid function with lithium use because treatment with a controlled substance carries an inherent risk of misuse, abuse, and diversion. For patients with SUDs, clinicians can explain that using UDTs to monitor their abstinence is similar to monitoring HbA1c for glucose control in patients with diabetes.
Continue to: Factors that can affect UDT results