Routine and random testing. Two common practices when treating addiction are to perform UDS on all patients, at every visit, or to test randomly.1 These practices can be problematic, however. Routine testing at every visit can make urine-tampering more likely and is often unnecessary for stable patients. Random testing can reduce the risk of urine-tampering, but it is often difficult for primary care clinics to institute such a protocol. Some clinics have patients provide a urine specimen at every visit and then only send tests to the lab based on randomization.1
Contingency management—a behavioral intervention in which a patient is rewarded, or their performance is reinforced, when they display evidence of positive change—is the most effective strategy used in addiction medicine to determine the frequency of patient visits and UDS.14,16 High-risk patients with self-reported active substance use or UDS results consistent with substance use, or both, are seen more often; as their addiction behavior diminishes, visits and UDS become less frequent. If addiction behavior increases, the patient is seen more often. Keep in mind that addiction behavior decreases over months of treatment, not immediately upon initiation.14,17 For contingency management to be successful, patient-centered interviewing and UDS will need to be employed frequently as the patient works toward meaningful change.14
The technology of urine drug screening
Two general techniques are used for UDS: immunoassay and chromatography. Each plays an important role in clinical practice; physicians must therefore maintain a basic understanding of the mechanism of each technique and their comparable advantages and disadvantages. Such an understanding allows for (1) matching the appropriate technique to the individual clinical scenario and (2) correctly interpreting results.
Immunoassay technology is used for point-of-care and rapid laboratory UDS, using antibodies to detect the drug or drug metabolite of interest. Antibodies utilized in immunoassays are designed to selectively bind a specific antigen—ie, a unique chemical structure within the drug of choice. Once bound, the antigen–antibody complex can be exploited for detection through various methods.
Chromatography–mass spectrometry is considered the gold standard for UDS, yielding confirmatory results. This is a 2-step process: Chromatography separates components within a specimen; mass spectrometry then identifies those components. Most laboratories employ liquid, rather than gas, chromatography. The specificity of the liquid chromatography–mass spectrometry method is such that a false-positive result is, essentially, impossible.18
Continue to: How is the appropriate tests elected for urine drug screening?