B-336 Comparison of the LZI Fentanyl Enzyme Immunoassay With ARKII and SEFRIA Fentanyl Assays on Beckman AU Analyzer
Authors: Manar S , George B , Huang R 
Published: September 2023

Abstract

Background
Fentanyl is a fast-acting synthetic opioid that can be prescribed for severe pain or found in illicit drugs. Routine clinical screening of fentanyl use is often performed on automated immunoassay analyzers, by measuring fentanyl and/or its primary metabolite, norfentanyl, in urine. Limited data has been published on performance of the relatively new LZI fentanyl enzyme immunoassay, which detects both fentanyl and norfentanyl but calibrated against norfentanyl. In this study, we evaluated the performance of LZI fentanyl assay on Beckman AU analyzer, in comparison to ARKII and SEFRIA assays calibrated against fentanyl.

Methods
The LZI and ARKII fentanyl assays were implemented on Beckman AU 5800 analyzer according to manufacturer’s instructions in our clinical laboratory. The LZI assay uses a cutoff value of 5 ng/mL for norfentanyl, while the ARKII assay uses a cutoff value of 1 ng/mL for fentanyl. The SEFRIA assay was performed on Beckman AU analyzer in a reference laboratory, with a cutoff value of 2 ng/mL for fentanyl. A qualitative comparison study was performed on a total of 42 deidentified urine samples, which were consecutively collected from clinical fentanyl screening test orders. Fentanyl screening results from the LZI and SEFRIA assays were available for all 42 samples, with ARKII results available for 28 out of the 42 samples. LC-MS confirmation test (cutoff value of 1 ng/mL for either fentanyl or norfentanyl) was also performed in a reference laboratory for samples with discrepant LZI results compared to either SEFRIA or ARKII results.

Results
A within day precision of &lt;10% (4.8%–9.7%) and between day precision of &lt;15% (7.0%–13.9%) were observed for the LZI fentanyl assay on Beckman AU analyzers, using calibrator or quality control samples at cutoff level, 25% lower and 25% higher than cutoff level. LZI and ARKII results agreed on 27 out of 28 samples (10 positive and 17 negative). Only one sample tested positive by ARKII but negative by LZI assay, which was also negative by SEFRIA and LC-MS. When compared to SEFRIA assay, results from LZI assay agreed on 35 out of 42 samples (10 positive and 25 negative). The seven discrepant results (negative on SEFRIA but positive on LZI) were all confirmed positive by LC-MS. The false negative results observed on SEFRIA were likely due to a cutoff value of 2 ng/mL instead of 1 ng/mL. There was one sample tested positive by LC-MS only (&lt;1.0 ng/mL for fentanyl and 3.3 ng/mL for norfentanyl), with inconclusive LZI results but counted as negative (positive on one instrument and negative on another). Overall, there was no false positive result reported by LZI assay in this study and 17 out of 18 positive samples were correctly identified, with a calculated sensitivity of 94%, specificity 100%, positive predictive value 100% and negative predictive value 96%.

Conclusion
The Beckman AU LZI fentanyl assay with a cutoff value of 5 ng/mL calibrated against norfentanyl has shown comparable performance as existing fentanyl assays and can be implemented for routine clinical screening of fentanyl.