Impact of Unconjugated estriol (uE3) assay interference on prenatal screening tests

• Published in: Clinica chimica acta Vol. 536; pp. 1 - 5
• Main Authors: Wyness, Sara P., Snow, Taylor M., Villanueva, Michelle, Kunzler, Theresa, Seiter, Jonathan, Genzen, Jonathan R., Johnson, Lisa M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2022
• Subjects: Antibody interference; Immunoassay; Prenatal screening; Unconjugated estriol; Immunoassay; uE3; ALP; Unconjugated estriol; MoM; Antibody interference; AFP; hALP; hCG; Prenatal screening; T18; Quad screen; DIA
• DOI: 10.1016/j.cca.2022.08.027
• ISSN: 0009-8981; 1873-3492

•We investigated interference of anti-alkaline phosphatase antibodies (anti-ALP’s).•The anti-ALP’s interfered with the unconjugated estriol assay for maternal serum screening.•These efforts identified 17 of 160 samples at increased risk for erroneous results.•Four of the 17 had screen interpretations changes using pseudo-risk calculations. Unconjugated estriol (uE3) is an important biomarker in second trimester prenatal screening. Previous studies from our laboratory identified rare interference in the Beckman uE3 assay due to anti-ALP antibodies, which could be mitigated with a scavenger or heat-inactivated ALP (hALP). In the current study, 160 de-identified patient samples previously submitted for the Quad screen with low uE3 multiples of the median (MoM ≤0.50) were investigated for potential interference. A reagent pack spiking strategy with hALP was employed to understand if the interference could be identified and mitigated in a scalable manner. The 160 samples were measured using uE3 lot #920861 previously known to be subject to interference, lot #920861 spiked with hALP, and the vendor reformulated lot #922579. Samples were suspected to have interference if the percent difference in uE3 measurements was >50%. Pseudo-risks were calculated using a test patient environment to understand the screening impact due to the change in uE3 result. Seventeen of the 160 samples had uE3 results that were >50% different between the hALP spiked and non-spiked reagent pack. Both original lot #920861 with hALP and reformulated lot #922579 identified the same 17 patients as having interference in lot #920861. Analysis of screening risks using a test patient environment showed that assay interference could result in false positives for one trisomy 21 and three trisomy 18 post-test risk calculations. Our experiment of reagent pack spiking with hALP produced similar uE3 results to a reformulated reagent designed to address potential interference, demonstrating that this is a feasible strategy to screen for interference in a scalable manner. The vendor-provided reformulation addressed anti-ALP interference and improved the performance of the screen.