Detection of 58 Fentanyl Analogs Using ARK Fentanyl II and Immunalysis Fentanyl Immunoassays

•Analysis of 58 fentanyl analogs as detected by the ARK II and Immunalysis fentanyl immunoassays.•Prediction of each immunoassay epitope allows for hypothesis of future analog detection.•Comparison of assay performance between the two vendors.•Comparison to native patient samples indicates both assays are sensitive and specific.•Both assays detect the majority of analogs indicating “false positive” screens that do not confirm for fentanyl may be detecting analogs instead.