Comparison of Two Rapid Urine Immunoassays for Xylazine Detection in Suspected Opioid Overdose Patients

Background: Xylazine, a veterinary sedative not approved for human use, is increasingly present, often mixed with fentanyl, in the illicit opioid supply.Its clinical impact in human overdose and methods for reliable detection remain unclear.To inform harm reduction strategies, this study evaluates and compares two rapid urine tests that can detect xylazine.Methods: This prospective observational study included emergency department (ED) patients with suspected opioid overdose at two New York City EDs between April and July 2025.Discarded urine samples from enrolled patients were tested for xylazine using two rapid immunoassays.The threshold of detection for the Instanosis Xylazine Test Strips was 1 ng/ml and for BTNX test strips, 1000 ng/ml.Results: Eleven urine samples were analyzed.Xylazine was detected in seven samples (64%) using the Instanosis Xylazine Test Strip.Only two samples (18%) had xylazine detected using the BTNX strips.Four samples (36%) tested negative using both strips. Conclusion:Preliminary findings highlight variability between test strips and suggest the need for further evaluation before determining clinical utility.These discrepancies may reflect false negatives with BTNX due to its higher detection threshold.Future work will compare xylazine serum testing with urine test strip testing.