B-324 Comparison of Two Urine Fentanyl Assays on the Abbott Alinity c Analyzer

Abstract

Abstract Background Mass spectrometry (MS) remains the gold standard, however immunoassays can provide a preliminary test result while the patient is still in the emergency room or clinic. Methods The ARK Fentanyl II assay (ARK Diagnostics Inc, Fremont, CA) was compared to the Immunalysis SEFRIA Fentanyl (Immunalysis Corporation, Pomona, CA) assay on the Abbott Alinity c analyzer (Abbott Park, IL) using leftover deidentified urine samples. MS analysis was performed at ARUP Laboratories (Salt Lake City, UT) to quantitate the amount of fentanyl or norfentanyl metabolite in each sample. 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 MS positive and 72 MS negative samples. Positive and negative assay specific 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. 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%. Upon repeat analysis, 4 of 4 ARK and 6 of 13 Immunalysis false positives reported as negative, indicating some variability around the cutoff concentration. Possible carryover from high samples has also been reported (ARK Technical Note 20-001-August 2020) and high samples were analyzed prior to some of the false positive samples. Six MS positive samples were reported as negative (false negatives), 3 samples by each of the assays. However, 4/6 of those samples had combined fentanyl and norfentanyl concentrations <3 ng/mL by MS. Conclusion The ARK Fentanyl II and Immunalysis SEFRIA assays demonstrated acceptable performance in the detection of fentanyl in our patient population.