Laboratory monitoring for patients on buprenorphine: 10 questions
How to best use laboratory testing for patients with opioid use disorder.
The presence of alcohol metabolites can alert the clinician to recent alcohol use and possible AUD, which should be assessed and treated if indicated.
Liver enzymes should be normal or unchanged with short- and long-term buprenorphine use when taken as prescribed.25,26 However, acute liver injury may occur if patients inject buprenorphine intravenously, especially in those with underlying hepatitis C.25
5. What can cause a false negative result on UDS?
Laboratory monitoring may occasionally yield false negative drug screens. For urine buprenorphine levels, false negatives may occur in patients who are “rapid metabolizers,” infrequent or as-needed usage of the medication, patient mix-up, or laboratory error.27 For other substances, a false negative result may occur if the patient used the substance(s) outside the window of detection. The most common causes of false negative results, however, are overly diluted urine samples (eg, due to rapid water ingestion), or the use of an inappropriate test to measure a specific opioid or substance.27
Many laboratories use conventional immunoassays with morphine antibodies that react with various opioid substrates to determine the presence of a specific opioid. Some opioids—particularly synthetics such as oxycodone, hydrocodone, hydromorphone, oxymorphone, fentanyl, buprenorphine, and methadone—have poor cross-reactivity with the morphine antibody due to their distinct chemical structures, so standard immunoassays used to detect opioids may result in a false negative result.28 In such situations, a discussion with a clinical pathologist familiar with the laboratory detection method can help ensure proper testing. Additional tests for specific opioids should be ordered to more specifically target substances prone to false negative results.27
6. What can cause a false positive result on UDS?
The cross-reactivity of the morphine substrate may also result in a false positive result.28 Other over-the-counter (OTC) or prescription medications that have cross-reactivity with the morphine antibody include dextromethorphan, verapamil, quinine, fluoroquinolones, and rifampin, which can normally be found in urine 2 to 3 days after consumption.17,27 Poppy seeds have long been known to result in positive opiate screens on urine testing, particularly when laboratories use lower cutoff values (eg, 300 ng/mL), so advise patients to avoid consuming poppy seeds.29
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