Lorazepam Detection with Urine Benzodiazepines Screening Tests: Not all Tests are Created Equal

Abstract

Abstract Lorazepam belongs to the benzodiazepines family of drugs and is one of the commonly used anti-anxiety medications in the US. In clinical practice, immunoassay screening tests are used to monitor compliance, detect abuse and in cases of drug overdose. Many clinicians rely on benzodiazepine immunoassay screening tests to detect lorazepam due to the test availability on automated clinical analyzers, short turnaround time and cost efficiency. However, compromised test sensitivity often leads to erroneous results. In this study, we used mass spectrometry to establish the lorazepam cross-reactivity threshold in two commonly used benzodiazepine screening tests: the Abbott ARCHITECT cSystem 16000 and NexScreen Drug Screen Cup. Methods: Mass spectrometry testing was performed at a major reference laboratory. Lorazepam-positive patient urine at concentrations of 320 ng/mL and 4,895 ng/mL were tested concurrently by two immunoassay methods. The Abbott ARCHITECT is a semi-quantitative assay with a positivity cut-off of 200 ng/mL. According to the manufacturer’s instructions for use (IFUs), the cross-reactivity threshold of the test is equivalent to a lorazepam concentration of 650 ng/mL. The NexScreen Drug Screen Cup is a lateral flow immunoassay used as a point-of-care (POC) test. The positivity cut-off of this test is 300 ng/mL; per IFUs, the cross-reactivity threshold of this test to lorazepam is 3,900 ng/mL, and 5,000 ng/mL for lorazepam-glucuronide, a drug metabolite. To determine the test sensitivity of the NexScreen test, patient specimen (4,895 ng/mL) was diluted at 1:5, 1:10, 1:20, 1:50, and 1:100, targeting the lorazepam concentrations of 979, 490, 245, 98 and 49 ng/mL respectively. To determine the sensitivity of the immunoassays to the parent molecule vs the metabolite, pre-screened negative urine was spiked with lorazepam or lorazepam-glucuronide at a concentration of 650 ng/mL, 5000 ng/mL, and 10000 ng/mL. Results: Abbott ARCHITECT failed to detect lorazepam in both patients, while the NexScreen resulted in positive benzodiazepine screen results for both patient specimens. All lorazepam-spiked specimens tested positive on both methods. However, all lorazepam glucuronide-spiked specimens tested negative on Abbott ARCHITECT and positive on NexScreen cup. The highest dilution detected by NexScreen was 1: 20, equivalent to approximately 245 ng/mL of lorazepam. Conclusion: Our findings suggest that the ARCHITECT benzodiazepine assay should not be used to screen patients on lorazepam, given its inability to detect the major metabolite, lorazepam glucuronide. Whenever available, a mass spectrometry method is always preferred. The results of our study demonstrated that in a specific patient population, where the likelihood of positive lorazepam test is high, the NexScreen cup is a viable, cost-effective alternative due to its excellent sensitivity.