Presumptive Tests for Xylazine – A Computer Vision Approach

Abuse of xylazine is an immediate global public health concern. We report the distinct and measurable colour changes when xylazine is exposed to the Mandelin, Marquis, and Mecke presumptive test reagents. The colour changes observed with xylazine are distinct from those of drugs that give colour changes from the same presumptive tests. Using single image and video analyses, distinctive features of presumptive tests with xylazine help differentiate it from other illicit substances tested under the same conditions, including morphine, fentanyl, heroin, and methamphetamine. Herein, experimental protocols utilising \textit{Kineticolor}, a computer vision software, were developed to qualitatively and quantitatively study presumptive tests for xylazine detection. To the best of our knowledge, these findings represent the first presumptive test strategy towards specific, quantifiable, and potentially field-ready detection of xylazine.