Development and Clinical Validation of a Sensitive Lateral Flow Assay for Rapid Urine Fentanyl Screening in the Emergency Department

BACKGROUND: Rapid identification of fentanyl at the point-of-care is critical. Urine fentanyl concentrations in overdose cases start at single-digit nanograms per milliliter. No fentanyl point-of-care assay with a cutoff at single-digit nanograms per milliliter is available. METHODS: A competitive lateral flow assay (LFA) was developed using gold nanoparticles and optimized for rapid screening of fentanyl in 5 minutes. Urine samples from 2 cohorts of emergency department (ED) patients were tested using the LFA and LC-MS/MS. The 2 cohorts consisted of 218 consecutive ED patients with urine drug-of-abuse screen orders and 7 ED patients with clinically suspected fentanyl overdose, respectively. RESULTS: The LFA detected fentanyl (>/=1 ng/mL) and the major metabolite norfentanyl (>/=10 ng/mL) with high precision. There was no cross-reactivity with amphetamine, cocaine, morphine, tetrahydrocannabinol, methadone, buprenorphine, naloxone, and acetaminophen at 1000 ng/mL and 0.03%, 0.4%, and 0.05% cross-reactivity with carfentanil, risperidone, and 9-hydroxyrisperidone, respectively. In 218 consecutive ED patients, the prevalence of cases with fentanyl >/=1 ng/mL or norfentanyl >/=10 ng/mL was 5.5%. The clinical sensitivity and specificity of the LFA were 100% (95% CI, 75.8-100%) and 99.5% (95% CI, 97.3-99.9%), respectively. The positive and negative predictive values were 92.3% (95% CI, 66.7-98.6%) and 100% (95% CI, 98.2-100%), respectively. The concordance between the LFA and LC-MS/MS was 100% in the 7 suspected fentanyl overdose cases (5 positive, 2 negative). CONCLUSIONS: The LFA can detect fentanyl and norfentanyl with high clinical sensitivity and specificity in the ED population with rapid fentanyl screening needs.