Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Understanding sensitivity and cross-reactivity of xylazine lateral flow immunoassay test strips for drug checking applications

Published

Author(s)

Edward Sisco, Madeline Bloom, Danielle Nestadt

Abstract

The continued prevalence of xylazine in the illicit drug market has necessitated development of quick and simple methods for identification, including lateral flow immunoassays (also known as "test strips"), like those frequently used to detect fentanyl. This study explored the drug checking applicability of the first publicly available xylazine test strips (XTS) using four sub-studies: reproducibility (i.e., consistency of positive results in a highly-concentrated xylazine solution); limit of detection on a calibration curve of xylazine concentrations; cross-reactivity against 77 commonly encountered drugs, cutting agents, and other structurally similar compounds; and applicability for analyzing community-acquired samples—where 100 drug residue samples were analyzed using XTS, direct analysis in real time mass spectrometry (DART-MS), and gas chromatography tandem mass spectrometry (GC–MS/MS). XTS consistently detected xylazine at concentrations ≥2.5 μg/ml, and XTS results were reproducible. Sensitivity and specificity of XTS were calculated by comparing expected versus obtained results based on xylazine concentration of community-acquired samples measured by GC-MS/MS. XTS consistently detected xylazine in samples with concentration >2 μg/ml and yielded a sensitivity of 0.974, specificity of 1.00, and overall accuracy of 0.986. Cross-reactivity with lidocaine, a common cutting agent, and lack of XTS reactivity with other α2-agonists found in the illicit drug supply highlight the need to offer consumers comprehensive drug checking services that identify a range of substances and better inform them about drug contents.
Citation
Drug Testing and Analysis

Citation

Sisco, E. , Bloom, M. and Nestadt, D. (2023), Understanding sensitivity and cross-reactivity of xylazine lateral flow immunoassay test strips for drug checking applications, Drug Testing and Analysis, [online], https://doi.org/10.1002/dta.3612, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936882 (Accessed April 19, 2024)
Created December 3, 2023, Updated March 27, 2024