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Comparison of a point-of-care serum amyloid A analyzer frequently used in equine practice with 2 turbidimetric immunoassays used in human and veterinary medicine.

Abstract: Rapid, accurate detection of serum amyloid A (SAA) is needed in equine practice. We validated a patient-side point-of-care (POC) assay (Stablelab; Zoetis) compared to the turbidimetric immunoassays LZ-SAA (TIA-Hum) and VET-SAA (TIA-Vet; both Eiken Chemical). Analytical performance was assessed at 3 different concentration ranges and with interferences. Inter-method comparison using 49 equine serum samples revealed a significant difference between median SAA results ( < 0.0001), with the strongest bias between the POC and TIA-Vet (median 1,093 vs. 578 mg/L). The median SAA value obtained with the TIA-Hum method was 752 mg/L. Correlation between POC/TIA-Hum and between POC/TIA-Vet was fair (r = 0.77 and 0.69) and excellent between both TIAs (r = 0.93). Bias between POC/TIA-Hum, POC/TIA-Vet, and TIA-Hum/TIA-Vet was -56.7%, -80.9%, and -28.2%, respectively. POC intra- and inter-assay CVs (16.1-30% and 19.8-35.5%) were higher than TIA CVs (generally 3,000 mg/L for the POC assay. Equine serum SAA was stable over a median period of 2.5 y when stored at -80°C. Overall, there was excellent-to-moderate correlation between tests, but imprecision and hook effect of the POC, as well as bias between the methods, must be considered.
Publication Date: 2021-11-11 PubMed ID: 34763564PubMed Central: PMC8688985DOI: 10.1177/10406387211056029Google Scholar: Lookup
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  • Journal Article

Summary

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The research paper investigates the performance of a point-of-care assay (Stablelab; Zoetis) for detecting serum amyloid A (SAA) in horses, comparing it with two turbidimetric immunoassays (LZ-SAA and VET-SAA), and reveals a significant difference between the two. It also points out various factors that could influence the tests’ accuracy like bilirubin, hemoglobin, and intralipid.

Study Design and Comparison

  • The researchers focused on validating a specific point-of-care (POC) assay, comparing its performance against two other tests used in both veterinary and human medicine. The tests were: LZ-SAA (Human Turbidimetric Immunoassay – TIA-Hum) and VET-SAA (Veterinary Specific Turbidimetric Immunoassay – TIA-Vet).
  • The analytical performance of these methods was evaluated across different concentration ranges.
  • A total of 49 equine serum samples were used for the inter-method comparison.

Findings and Observations

  • The research demonstrated a significant difference between the median SAA results produced by the different methods, indicating that the results produced by the POC and TIA-Vet are consistently different.
  • Statistical analysis showed fair correlation between the results of POC/TIA-Hum and POC/TIA-Vet and excellent correlation between those of both TIAs.
  • However, there was a “bias” between all combinations of the methods, meaning that one consistently estimated higher or lower than the others.
  • POC had a higher variability in terms of intra- and inter-assay CVs (Coefficient of Variation) compared to the TIAs.
  • They also found that bilirubin and hemoglobin have a negative impact on the results of the POC and TIA-Vet tests, while the addition of intralipid showed a positive bias.
  • The overall linearity of the SAA concentrations was good for POC up to 10,312 mg/L, but a hook effect was found at concentrations of SAA greater than 3,000 mg/L.
  • Stability testing found horse serum SAA to remain stable over a period of 2.5 years when stored at -80°C.

Conclusion and Implications

  • While there is a moderate to excellent correlation between the different tests, the study underscores multiple considerations. This includes the imprecision and hook effect of the POC when SAA concentration is high, and the discrepancies (or biases) among the three methods.
  • The insights might caution the interpretation of absolute SAA values acquired from different methods and potential interferences that can impact it.

Cite This Article

APA
Kiemle J, Hindenberg S, Bauer N, Roecken M. (2021). Comparison of a point-of-care serum amyloid A analyzer frequently used in equine practice with 2 turbidimetric immunoassays used in human and veterinary medicine. J Vet Diagn Invest, 34(1), 42-53. https://doi.org/10.1177/10406387211056029

Publication

ISSN: 1943-4936
NlmUniqueID: 9011490
Country: United States
Language: English
Volume: 34
Issue: 1
Pages: 42-53

Researcher Affiliations

Kiemle, Julia
  • Clinic for Horses, Department of Equine Surgery and Orthopaedics, Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Giessen, Germany.
Hindenberg, Sarah
  • Department of Veterinary Clinical Sciences, Clinical Pathology and Clinical Pathophysiology, Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Giessen, Germany.
Bauer, Natali
  • Department of Veterinary Clinical Sciences, Clinical Pathology and Clinical Pathophysiology, Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Giessen, Germany.
Roecken, Michael
  • Clinic for Horses, Department of Equine Surgery and Orthopaedics, Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Giessen, Germany.

MeSH Terms

  • Animals
  • Horses
  • Humans
  • Immunoturbidimetry / veterinary
  • Point-of-Care Systems
  • Serum Amyloid A Protein

Conflict of Interest Statement

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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Citations

This article has been cited 2 times.
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