MEDICAL INNOVATIONS
More Than a Test for Illicit Drugs: Utilization of Urine Drug Tests to Manage Patients By James Shurko, PharmD, PhD and Niti Vanee, PhD
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linicians are faced with a number of challenges on a daily basis. When treating patients, they are tasked with evaluating medication safety and effectiveness, assessing medication adherence and identifying medication diversion. In some cases, the effectiveness of medications can easily be observed by simple physical assessment e.g., ACE inhibitors and blood pressure. In other instances, however, treatment relies heavily on patient response to subjective rating scales. Treatment with analgesics and anti-depressants are prime examples. Medication non-adherence is a common problem with 20-30% of prescriptions remaining unfilled and 50% of medications used for the treatment of chronic diseases being taken in a manner other than prescribed. Further, healthcare costs due to nonadherence have been reported as approximately $20,000 per patient per year and upwards of $300 billion annually.1,2 Finally, drug diversion, characterized by the sale, loss or theft of medication has been reported in 45% of patients and is common in many medications including opioids and benzodiazepines.3 These challenges pose problems for clinicians when creating or modifying a current drug regimen since the medications are not being utilized as assumed. Urine drug testing through antibody-based screens and chromatography-based confirmation offer a way to assess medication utilization and therefore serve as a tool to mitigate these challenges. The concept of medication monitoring is well established. Digoxin levels, prothrombin times, vancomycin troughs and non-protein bound phenytoin levels represent a mere fraction of the instances in which 30
SAN ANTONIO MEDICINE • May 2022
medications are monitored. Notably, these practices all require blood tests and can be invasive, especially in the outpatient setting where drawing from an IV is rarely an option. Herein lies the value of urine drug testing (UDT). While UDT is commonly employed in the work, sporting or legal arenas, these tests can be implemented by clinicians seeking to gain insight into medication effectiveness and evaluate medication utilization in scenarios when blood testing is not an ideal option or commonly practiced. Comparatively, UDT are relatively easy to implement and non-invasive. For example, urine drug screens (UDS) can be performed as a point of care test by using urine testing cups. These tests work through immunochromatography in which antigen linked compounds are separated by capillary beds and then detected through binding with corresponding antibodies.4 Positive tests can then be sent for further analysis as a “reflex” test for confirmation. Alternatively, urine cups or tubes can be sent directly to toxicology labs to identify specific compounds. These compounds are generally identified in a two-stage manner. First, a screening method, such as an antibody/antigen-based immunoassay is conducted to detect drugs or metabolites within a panel of compounds. Second, a confirmatory test is performed. Confirmatory tests are performed to account for limitations associated with UDS. Despite incorporating sample validity tests to identify adulteration such as urine creatinine, nitrites, pH and specific gravity, UDS can still be affected by masking agents leading to a negative result. Additionally, UDS are prone to false positive results due to cross-reactivity. For example, ibuprofen has been shown to crossreact with and lead to false positive tests for barbiturates and THC.5
