B-270 Comparison of a New Rapid Drug Test Device against Two Urine Fentanyl Immunoassays on the Abbott Alinity c Analyzer
Authors: Laryea E , Nichols J H 
Published: October 2024

Abstract

Background
Mass spectrometry (MS) remains the gold standard for assessing the presence of fentanyl and its metabolites in urine. However, immunoassays for measuring urine fentanyl and its metabolites have been developed with faster turnaround time. A new point-of-care testing (POCT) method, the Rapid Drug Test Device (RDTD), is now available for urine fentanyl testing. Immunoassays and POCT can provide a preliminary test result while the patient is still in the emergency room or clinic. We evaluated the analytical performance of the ARK and Immunalysis Fentanyl urine immunoassays on the Abbott Alinity c analyzer compared to the RDTD for urine fentanyl.

Methods
The analytical performance of the ARK Fentanyl II assay (ARK Diagnostics Inc, Fremont, CA) and the Immunalysis SEFRIA Fentanyl assay (Immunalysis Corporation, Pomona, CA) was compared to the RDTD for urine fentanyl (CLIA Waived, Inc. Carlsbad, CA) using leftover deidentified urine samples collected from our patient population. Samples were stored frozen at &lt;-70°C, thawed at room temperature, centrifuged, and aliquots analyzed by both immunoassays on the Abbott Alinity c chemistry analyzer and the visual RDTD POCT device. MS analysis was performed at ARUP Laboratories (Salt Lake City, UT) to quantitate the amount of fentanyl or norfentanyl in each sample. Assay sensitivity, specificity, positive predicative value (PPV), negative predictive value (NPV), and efficiency were calculated using a 1 ng/mL positive cutoff for all tests. Medications prescribed at the time of sampling were reviewed to assess for possible cross reactivity with the assays.

Results
A total of 142 urine samples were analyzed with 70 positive and 72 negative samples by MS. Positive and negative quality control precision (N=10) was 3.0% and 9.6% CV for the ARK Fentanyl II assay and 10.2% and 15.9% CV for the Immunalysis SEFRIA assays respectively. Qualitative controls were analyzed with each batch of samples on the RDTD. The ARK Fentanyl II assay showed identical sensitivity to the Immunalysis SEFRIA assay but had higher specificity and overall efficiency for the samples from our patient population. ARK Fentanyl II Sensitivity = 95.7%, Specificity = 94.4%, PPV = 94.4%, NPV = 95.8% and Efficiency = 95.1% compared to the Immunalysis SEFRIA Fentanyl Sensitivity = 95.7%, Specificity = 81.9%, PPV = 83.8%, NPV = 95.2% and Efficiency = 88.7%. The Rapid Drug Test Device showed lower sensitivity = 84.3% and specificity = 87.5%, PPV = 86.8%, NPV = 85.1% and Efficiency = 85.9%.

Conclusions
The ARK Fentanyl II, Immunalysis SEFRIA immunoassays and the RDTD demonstrated acceptable performance in the detection of fentanyl and it's metabolites in our patient population. Differences were noted in the number of false positives between the assays on these samples as well as six samples that were missed (false negatives), 3 samples by each of the immunoassays and 11 by the RDTD. However, 4/6 of those samples had combined fentanyl and norfentanyl concentrations &lt; 3 ng/mL by MS or 11/11 samples &lt; 7 ng/mL by MS for the RDTD. Laboratories should assess the acceptability of drug screen immunoassay performance using samples from their patient populations.