Pain Management: Urine Drug Testing
In 2009, the American Pain Society and American Academy of Pain Management published recommendations from a multidisciplinary expert panel for the use of chronic opioid therapy (COT) for chronic non-cancer pain in primary care and specialty settings. The guideline acknowledges the importance of periodic urine drug testing to identify undisclosed drug use and/or abuse in patients administered COT at high risk for abuse or diversion. Additionally, the guideline recognizes the utility of urine drug testing in patients at low risk for abuse or diversion as a means of monitoring adherence to prescribed therapy.
Urine drug testing is a preferred screening method due to ease of use and low cost. Although widely available and routinely used, accurate interpretation of urine drug testing results requires the health care provider to understand urine drug testing limitations related to test sensitivity/specificity as well as factors that may influence test results.
Urine Drug Testing Methods
The two main types of urine drug testing are immunoassay testing and laboratory-based testing [e.g., gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), or high performance liquid chromatography (HPLC)]. Immunoassay tests use antibodies to identify the presence or absence of a specific drug or metabolite and are commercially available as point of care devices or home-testing kits. Disadvantages of immunoassay tests include false-positive results and the variability in the range of drugs identified (i.e., some identify specific drugs, while others identify classes of drugs). Based on known disadvantages, the results of immunoassay tests are usually considered presumptive until confirmed by a laboratory-based test (e.g., GC/MS). Laboratory-based tests are capable of identifying the presence of a specific drug and are considered the standard for confirmatory testing. However, unlike immunoassays tests, they are time-consuming, expensive, and require skilled personnel to perform the test.