Validation of an automated immunoturbidimetric assay for feline serum amyloid A

Waugh, E. M., Haining, H., Harvie, J., Ridyard, A. E. and Eckersall, P. D. (2022) Validation of an automated immunoturbidimetric assay for feline serum amyloid A. BMC Veterinary Research, 18, 359. (doi: 10.1186/s12917-022-03456-5) (PMID:36171578) (PMCID:PMC9516510)

Abstract

Background Serum Amyloid A (SAA) is a major acute phase protein in cats, increasing rapidly in response to various inflammatory diseases. An automated latex-enhanced immunoturbidimetric assay for human SAA (LZ-SAA, Eiken), previously validated for use in cats, has had further major modification (VET-SAA, Eiken) for specific use in veterinary diagnostic laboratories but has yet to be validated in cats. Results Intra-assay and inter-assay CVs for the VET-SAA assay ranged from 1.88–3.57% and 3.98–6.74%, respectively. Linearity under dilution was acceptable with no prozone effect observed. Limit of detection was 1.65 mg/L and limit of quantification was 6 mg/L. Haemoglobin and triglyceride showed no adverse interference, but bilirubin produced positive bias in samples with low SAA. Comparison with the LZ-SAA assay showed significant correlation with proportional bias increasing as SAA concentration increased, likely related to differing calibration standards. SAA was significantly higher in patients with inflammatory disease compared with non-inflammatory disease, and in patients with moderate to highly elevated α1-AGP compared with patients with normal α1-AGP. Improvement of the assay range may be required to fully evaluate differences between disease groups at low SAA levels. Based on ROC curve analysis, at a cut-off point of 20.1 mg/L the VET-SAA assay discriminated between inflammatory and non-inflammatory disease with sensitivity of 0.93 and specificity of 0.99. Conclusions The automated VET-SAA assay is a robust, precise, and accurate method for measurement of feline SAA which can clearly identify patients with inflammatory disease. It should be a valuable biomarker for use in feline medicine.

• Item Type: Articles
• Additional Information: The study was funded by Eiken Chemical Co, Tokyo, Japan, who also provided reagents and assisted with initial set-up of the assay.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Eckersall, Professor David and Ridyard, Ms Alison and Harvie, Mr James and Waugh, Ms Elspeth and Haining, Dr Hayley
• Authors: Waugh, E. M., Haining, H., Harvie, J., Ridyard, A. E., and Eckersall, P. D.
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: BMC Veterinary Research
• Publisher: BioMed Central
• ISSN: 1746-6148
• ISSN (Online): 1746-6148
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in BMC Veterinary Research 18: 359
• Publisher Policy: Reproduced under a Creative Commons License