Evaluation of a Benzodiazepine Immunoassay for Urine Drug Testing in Clinical Specimens

Abstract

Background: Benzodiazepines are commonly prescribed medications frequently linked to instances of abuse and overdose. Historically, FDA-cleared benzodiazepine urine immunoassays cross-react poorly with glucuronidated benzodiazepine metabolites, leading to false negatives. Clinical laboratories have addressed this deficiency by creating laboratory-developed tests (LDTs) that incorporate a beta-glucuronidase hydrolysis step to increase the clinical sensitivity of these assays. Methods: Performance characteristics of 2 FDA-cleared benzodiazepine urine immunoassays (Benzodiazepines Plus, no glucuronidase and Benzodiazepines II, with glucuronidase; Roche Diagnostics) and a previously described benzodiazepine immunoassay LDT (with glucuronidase) were evaluated using 258 clinical urine specimens. The positive immunoassay cutoff was set at 200 ng/mL of nordiazepam and results were compared to an LC-MS/MS benzodiazepine LDT. Clinical sensitivity, specificity, precision, and immunoassay cross-reactivity were determined for all 3 immunoassays. Results: The Benzodiazepines II and LDT immunoassays exhibited greater clinical sensitivity (100% and 95.2%) compared to the Benzodiazepines Plus assay (66.7%). Clinical specificity of 100% was observed for all 3 assays. Immunoassay response of the Benzodiazepines II assay was greater across the range of concentrations tested (100-1000 ng/mL) relative to the other immunoassays and was the most sensitive immunoassay for the detection of lorazepam glucuronide. Conclusions: The Benzodiazepines II immunoassay demonstrated the greatest clinical and analytical sensitivity compared to the Benzodiazepines Plus and LDT immunoassays. The incorporation of beta-glucuronidase was crucial, as the Benzodiazepines II and LDT immunoassays demonstrated superior clinical sensitivity when compared to the Benzodiazepines Plus immunoassay that does not incorporate a beta-glucuronidase hydrolysis step.