MSACL 2024 Abstract

Fentanyl Urine Drug Screen Comparison of the Ark II and Lin Zhi FEN2 Immunoassays

K.H. Brian Lam1, Marlen Menlyadiev2,3, Vincent Buggs1, Suttida, Parnprome1, Amadeo Pesce4, Raymond T. Suhandynata3,5, Robert L. Fitzgerald3, Lu Song1, Imir G. Metushi1
(1) Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, United States of America (2) Geisinger Health System, Danville, PA, USA (3) Department of Pathology, Center for Advanced Laboratory Medicine, University of California, San Diego Health Systems, San Diego, CA, United States (4) Precision Diagnostics, LLC, San Diego, CA, United States (5) Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, San Diego, CA, United States

Brian Lam, PhD (Presenter) University of California Los Angeles

Relevant Financial Disclosures (within past 24 months, reported on Sep 11, 2023) No relevant financial relationship(s) to disclose. Conflict mitigation NOT REQUIRED.

Background: Given the opioid epidemic, fentanyl screening in urine has become increasingly important. Immunoassays remain the most common screening methodology due to the high throughput and ease of integration into automated chemistry systems. The ARK II is a widely used immunoassay, while a novel assay, FEN2 by Lin Zhi, has become available on the Roche platform; here, we evaluate and compare their performance.

Methods: 457 urine samples were analyzed for fentanyl across the FEN2 and ARK II assay on the Cobas c502 platform. Samples were analyzed immediately upon request for drug of abuse screening or frozen for subsequent analysis. For confirmation testing, a liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) method with a limit of detection of 1 ng/mL for fentanyl/norfentanyl was used. Any sample with either fentanyl or norfentanyl above the LC-MS/MS cut-off was deemed positive.

Results: Both the ARK II and FEN2 immunoassays adequately detected fentanyl. The ARK II had a sensitivity and specificity of 86.0 and 96.6, respectively, and FEN2, with a sensitivity and specificity of 87.5 and 98.4, respectively.

Conclusion: The current data set has some discrepant results between the ARK II and Lin Zhi immunoassays. Most of the discrepant results have concentrations of fentanyl and norfentanyl near the cut-off for immunoassay detection.