Despite the improved clinical sensitivity of the Roche benzodiazepines II assay it cannot replace mass spectrometry in all patient populations.

Introduction: Benzodiazepines are frequently prescribed and misused therefore urine drug screening (UDS) is performed in many patient populations. Most current benzodiazepine immunoassays have poor sensitivity, particularly for detecting the metabolites of newer benzodiazepines such as lorazepam in urine. Objectives: We aimed to verify the clinical performance of the new qualitative Roche Benzodiazepines II (BNZ2) immunoassay, as well as compare its performance to the Roche Benzodiazepines Plus (BENZ) assay in two patient populations: UDS in the emergency department (ED) and compliance monitoring. Methods: An initial verification study was performed, selecting for samples containing clonazepam and lorazepam metabolites. Performance of the BNZ2 and BENZ assays was compared to liquid chromatography-tandem mass spectrometry (LC-MS/MS) as the reference method. Sensitivity, specificity, false positive rate (FPR) and false negative rate (FNR) were determined. Results: We verified the performance claims in the initial verification and demonstrated similar precision, with coefficient of variations (CVs) of 12.8% and 7.7% for negative and positive controls, respectively. Furthermore, we observed higher clinical sensitivity and lower FNR with the BNZ2 assay in both the ED and compliance monitoring populations due to improved cross-reactivity for lorazepam and clonazepam metabolites. Despite these improvements, the BNZ2 assay was unable to detect 27% of specimens positive by LC-MS/MS, including specimens from patients using benzodiazepines without prescription. Discussion: Due to its improved performance and rapid turnaround time, the BNZ2 assay should be implemented for UDS in the ED. However, the assay should not replace LC-MS/MS testing for compliance monitoring, as unsuspected benzodiazepine use may go undetected.

Performance of a Norfentanyl Immunoassay in Specimens with Low Concentrations of Fentanyl and/or Norfentanyl.

BACKGROUND: Many fentanyl immunoassays are limited in their ability to detect norfentanyl. Urine specimens collected from individuals who have been exposed to fentanyl frequently have detectable concentrations of norfentanyl (≥2 ng/mL) but low concentrations of fentanyl (<2 ng/mL) by LC-MS/MS. The Lin-Zhi Fentanyl II Immunoassay (Lin-Zhi) claims 100% cross-reactivity with norfentanyl and therefore may detect exposure missed by other assays. METHODS: In addition to verifying the manufacturer's analytical sensitivity claims, we selected 92 urine specimens with low-positive Lin-Zhi results (1-99 absorbance units, lowest 10%) for analysis by the Immunalysis Health Equity Impact Assessment and ARK II fentanyl methods. The accuracy of the 3 immunoassays was compared to LC-MS/MS as the reference method. RESULTS: Spiking studies using purified fentanyl and norfentanyl and a set of 100 consecutive specimens confirmed the manufacturer's claims of limit of detection for fentanyl (3.8 ng/mL) and norfentanyl (5.0 ng/mL). However, the 92 low-positive patient specimens demonstrated concentrations of norfentanyl and fentanyl below 2.0 ng/mL by LC-MS/MS, with 47 (51%) having only norfentanyl detected. When comparing Lin-Zhi to the Immunalysis and ARK II immunoassays, only 27 (29%) of the 92 specimens were concordant. Fifty-two (57%) of the specimens were positive by LC-MS/MS and Lin-Zhi but false negative by one or both other immunoassays. Seven specimens (8%) were positive by Lin-Zhi but negative by the other immunoassays and had undetectable concentrations (<2 ng/mL) of fentanyl and norfentanyl by LC-MS/MS. CONCLUSIONS: The clinical sensitivity of the Lin-Zhi exceeds the manufacturer's claims, providing results comparable to LC-MS/MS methods.