Urine drug screening: A guide to monitoring Tx with controlled substances
Avoid error by ordering the appropriate test at a risk-based frequency. Be alert to sources of false-positives and adulteration. Be careful not to overreact to unexpected results.
PRACTICE RECOMMENDATIONS
› Consider developing a risk-based urine drug testing protocol for all patients who are on chronic opioid therapy. C
› Consider urine drug testing to augment a thorough history when identifying and offering treatment to patients with a substance use disorder. A
› Do not change your management plan based on results of a single screening urine test. Revisit unexpected positive or negative results with a thorough history or confirmatory testing. A
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
How is the appropriate tests elected for urine drug screening?
Variables that influence your choice of the proper test method include the clinical question at hand; cost; the urgency of obtaining results; and the stakes in that decision (ie, will the results be used to simply change the dosage of a medication or, of greater consequence, to determine fitness for employment or inform criminal justice decisions?). Each method of UDS has advantages that can be utilized and disadvantages that must be considered to obtain an accurate and useful result.
Immunoassay provides rapid results, is relatively easy to perform, and is, comparatively, inexpensive.1,14 The speed of results makes this method particularly useful in settings such as the emergency department, where rapid results are crucial. Ease of use makes immunoassay ideal for the office, where non-laboratory staff can be trained to properly administer the test.
A major disadvantage of immunoassay technology, however, is interference resulting in both false-positive and false-negative results, which is discussed in detail in the next section. Immunoassay should be considered a screening test that yields presumptive results.
Liquid chromatography–mass spectrometry is exquisitely specific and provides confirmatory test results—major advantages of the method. However, specificity comes at a price: significantly increased cost and longer wait time for results (typically days, if specimens are sent out to a laboratory). These barriers can make it impractical to employ this method in routine practice.
Interpretation of results: Not so fast
Interpreting UDS results is not as simple as noting a positive or negative result. Physicians must understand the concept of interference, so that results can be appropriately interpreted and confirmed. This is crucial when results influence clinical decisions; inappropriate action, taken on the basis of presumptive results, can have severe consequences for the patient–provider relationship and the treatment plan.1,14
Continue to: Interference falls into 2 categories...
