If there’s one lab test that’s most overrated and misunderstood, it’s urine drug testing.
It is frequently requested when evaluating psychiatric patients, those with altered mental status, and those who may have an overdose. Some doctors even order urine drug screening to assess chest pain, abdominal pain, and dizziness. A typical drug test for amphetamines, cocaine, marijuana, opioids, and benzodiazepines, but some may also include phencyclidine and tricyclic antidepressants. (Mayo ClinProc. 2017;92:774; https://mayocl.in/3QgKjT7.)
A doctor may know the limitations of a urine drug test, but order it anyway. It’s usually quick to execute and many believe that adds to the toll. Unfortunately, this is not only a dismal diagnostic test, but it also harms patients.
Urine drug screening is a collection of immunoassays that relies on an interaction between the structure of a particular drug, metabolite, or antibody. Drugs being tested may bear structural similarity to those not being tested, leading to false positives. Amphetamines, for example, are structurally similar to some antihistamines and even cough and cold syrups, so a patient taking cetirizine may be flagged as positive for amphetamines on a urine drug screen. (Mayo ClinProc. 2017;92:774; https://mayocl.in/3QgKjT7.) The structure of diphenhydramine, hydroxyzine and quetiapine is similar to the structure of tricyclic antidepressants and can also cause false positives. Many articles in the emergency medicine literature give many other examples.
Drugs tested may also have enough structural alterations to cause a high level of false negatives. Fentanyl and synthetic cannabinoids do not show up on a urine drug screen. (Psychopharmacology [Berl]. 2013;228:525; https://bit.ly/3zQ5swb.) Other synthetic creations or designer drugs can contain a variety of additives and fillers, which also makes them virtually undetectable. (Mayo ClinProc. 2008;83:848; https://mayocl.in/3AbxKTh.) Benzodiazepines have a 25-30% false negative rate. (Mayo ClinProc. 2017;92:774; https://mayocl.in/3QgKjT7.) The lack of sensitivity and specificity makes urine drug screening a presumptive test at best.
Makes little difference
A urine drug screen provides qualitative data, not a quantitative result, which severely limits its accuracy. These urine tests do not provide information about how much of a drug is in a patient’s body or how long a patient has been using it. Most drugs are undetectable in urine after 72 hours, so the duration of an average urine drug screen is short. It should play a minimal role, if any, in routine clinical decision-making.
American College of Emergency Physicians clinical policy states that urine drug screening should not be performed in alert, awake, and cooperative patients with acute psychiatric symptoms, as it does not alter emergency management . (Ann Emergency Med. 2017;69:480; https://bit.ly/3STzKXU.) Unfortunately, many inpatient psychiatric centers require one for admission.
No adult or pediatric studies have shown that urine drug screening alters patient care. (Pediatric emergency care. 1997;13:194; Australian psychiatry. 2015;23:128.) They actually increase a patient’s length of stay (J Med Urgent. 2018;5:500) and rarely provide timely practice-modifying management for critically ill or impaired patients. (Clin Toxicol [Phila]. 2009;47:286.) False positives caused by a urine drug screen could lead to further downstream testing being inappropriate and harmful to the patient.
More harm than good
That’s not the only harmful thing about it. No other diagnostic test in the emergency department, aside from the sexually transmitted disease test (which is accurate), has as many implications for reputation, sports participation, professional status, and even belief in a patient. A positive urine drug screen does not indicate a substance use disorder, but healthcare professionals may let it implicitly change the way they care for a patient.
An obstetric study of 8,487 live-born women found that black women and their newborns were 1.5 times more likely to be tested for illicit drugs than women of other races. (J Women’s Health [Larchmt]. 2007;16:245; https://bit.ly/3bQs4F1.) One can imagine the adverse consequences, such as inappropriate referrals to child protective services, based on a presumptive test with the potential for false positives.
Another study by the US Department of Veterans Affairs Chronic Pain Clinic of 15,000 patients (48% black, 52% white) was revealing. Black patients who tested positive for cannabinoids in a urine drug screen were 2.1 times more likely than whites to have their long-term opioid treatment discontinued. Black patients who tested positive for cocaine were 3.3 times more likely. (Alcohol addiction. 2018;192:371; https://bit.ly/3bL2VLU.)
Evidence from previous studies has shown that non-Hispanic black patients were already less likely to receive opioid prescriptions for back and abdominal pain compared to white patients, so it seems possible that a positive drug screen in the Urine further contributes to this disparity. (PLoS One. 2016;11:e0159224; https://bit.ly/3QmhJ2O.)
Encountering patients who abuse substances is a daily occurrence in emergency medicine. We need to be compassionate at the bedside instead of being confrontational or ordering a urine drug screen to catch a patient in the act. Connect with each patient and build a rapport. Displaying non-judgmental affect is essential when discussing substance abuse with patients.
Emergency physicians are the ultimate patient advocates. No other specialty sees the diverse and often vulnerable patient population we encounter daily. Ordering such an imprecise diagnostic test that does not change patient care and potentially creates bias is not our ethical duty. Be a patient advocate and realize you can’t rely on unnecessary urine drug testing.
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Dr. Briggsis an assistant professor of emergency medicine at the University of Tennessee Medical Center in Knoxville. He is the founder, a podcast host and the editor of EM Board Bombs (https://www.emboardbombs.com), a cross-platform educational tool designed to provide board preparation and focus on what EPs need to know for the practice of emergency medicine. Follow him on Twitter@blakebriggsmd.