Determining the detection of 216 fentanyl analogs and synthetic opioids and predicting epitopes using four commercial immunoassays.

BACKGROUND

The United States continues to face a persistent opioid epidemic, now in its fourth wave, characterized primarily by fentanyl analogs. Detecting fentanyl analogs and synthetic opioids is a critical concern to clinical and forensic laboratories.

OBJECTIVES

Evaluate the ability of each assay to detect the opioids at 1, 10, or 100 ng/mL. 216 opioids from the CDC's TOM Kits® were evaluated using four commercially available fentanyl immunoassays: ARK™ Fentanyl II, Immunalysis Fentanyl Urine HEIA®, Immunalysis Fentanyl Urine SEFRIA® Drug Screening Kit, and the Lin-Zhi International Fentanyl II Enzyme Immunoassay.

RESULTS

The difference in reactivity of the immunoassay's reagents was evaluated in conjunction with the chemical structure of each opioid. All four immunoassays detected 106 of the 216 opioids at the concentrations tested. Twenty-eight opioids were not detected by any assay and 17 of these were the emerging synthetic opioids. At the lowest concentration tested (1 ng/mL), the ARK™ Fentanyl II assay detected 36 compounds, the Immunalysis SEFRIA® assay detected 74, LZI detected 5, and the Immunalysis HEIA® assay detected 18. The undetected opioids included the surgical anesthetic parent compounds remifentanil and alfentanil, and sufentanil's metabolite, norsufentanil.

CONCLUSIONS

The detectability of fentanyl analogs and synthetic opioids varies by assay, and it may be possible to predict the detection or lack thereof for a particular assay based on a pattern elucidated by the analysis of the TOMs Opioid compound set. This data may be used to evaluate the potential false negative or false positive results of commercially available fentanyl and norfentanyl homogeneous immunoassays and to predict the likely target epitope of each assay.