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Journal of veterinary internal medicine2025; 39(2); e70038; doi: 10.1111/jvim.70038

Evaluation of an Automated Fluorescence Enzyme Immunoassay for Quantification of Equine Insulin and Comparison to Five Other Immunoassays.

Abstract: Hyperinsulinemia is an important and treatable risk factor for laminitis in horses. Objective: Evaluate the Tosoh AIA-360 automated fluorescence enzyme immunoassay for the measurement of serum insulin concentrations in horses, and compare it to five other immunoassays for insulin quantification. Methods: One hundred serum samples from 83 horses were submitted for insulin measurement. Methods: The Tosoh AIA-360 was assessed against a reference assay (radioactive immunoassay; RIA). Using the same samples, TOS-FEIA, ELISA, and three chemiluminescent immunoassays (CLIA) were assessed for correlation and agreement with RIA. Results: The TOS-FEIA showed excellent correlation with RIA (r = 0.94, p < 0.0001) and good agreement, with a Bland-Altman constant bias (limits of agreement) of -23.8 μIU/mL (-74.6 to 27.0) and Passing-Bablok fit of y = -8.9 + 0.78x. Mean coefficients of variation were 1.8% for intra-assay and 5.7% for inter-assay precision, with mean recovery upon dilution of 104.2%. The assay comparison yielded good or excellent agreement (constant bias, limits of agreement) with RIA in the  10-fold of RIA result) were obtained in approximately 10% of results from both Immulite 2000 and 2000XPi CLIA analyzers, rendering the agreement poor. Conclusions: The TOS-FEIA had acceptable accuracy and precision for clinical use, including at concentrations of insulin < 100 μIU/mL. The ELISA and one CLIA (Cobas e) showed acceptable accuracy, but the Cobas e demonstrated marked bias compared with RIA. Both Immulite CLIA assays exhibited unacceptable accuracy.
© 2025 The Author(s). Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.
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Publication Date: 2025-03-06 PubMed ID: 40048611PubMed Central: PMC11884604DOI: 10.1111/jvim.70038Google Scholar: Lookup
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  • Journal Article
  • Comparative Study
  • Evaluation Study

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The study evaluates the efficiency of the Tosoh AIA-360, an automated fluorescence enzyme immunoassay, in measuring serum insulin concentrations in horses and compares its efficiency with five other immunoassays. The authors find that the Tosoh AIA-360 shows high correlation and good agreement with a reference immunoassay.

Methodology

  • The study involved 100 serum samples obtained from 83 horses.
  • The prime focus was to evaluate the Tosoh AIA-360 automated fluorescence enzyme immunoassay (TOS-FEIA) to measure equine insulin. It was compared with the reference assay – radioactive immunoassay (RIA).
  • This comparison also involved the use of other assays namely, ELISA (Enzyme-linked immunosorbent assay) and three chemiluminescent immunoassays (CLIA). All these were assessed for correlation and agreement with RIA.

Results

  • The Tosoh AIA-360 demonstrated high correlation (r=0.94, p<0.0001) with the reference assay and showed excellent agreement in results.
  • There was good intra-assay and inter-assay precision, with mean coefficients of variation recorded at 1.8% and 5.7% respectively.
  • On average, the dilution recovery rate was 104.2%.
  • The study also found good or excellent agreement between RIA and the ELISA, and the Cobas e CLIA immunoassays within the less than 100 μIU/mL cohort.
  • Nevertheless, the Cobas e CLIA showed significant bias compared to the RIA.
  • About 10% of results from the Immulite 2000 and 2000XPi CLIA analyzers showed spuriously high results—2 to more than 10 times the RIA result. This led to poor agreement between these analyzers and the reference assay.

Conclusions

  • Overall, the Tosoh AIA-360 was deemed to have acceptable accuracy and precision, even at insulin concentrations less than 100 μIU/mL, making it suitable for clinical use.
  • While the ELISA and Cobas e CLIA also showed acceptable accuracy, Cobas e CLIA demonstrated marked bias when compared with the reference assay.
  • The Immulite CLIA assays were noted for their unacceptable level of accuracy when assessed against the reference assay.

Cite This Article

APA
Nolen-Walston RD, Kulp JC, Stefanovski D, van Eps AW. (2025). Evaluation of an Automated Fluorescence Enzyme Immunoassay for Quantification of Equine Insulin and Comparison to Five Other Immunoassays. J Vet Intern Med, 39(2), e70038. https://doi.org/10.1111/jvim.70038

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 39
Issue: 2
Pages: e70038
PII: e70038

Researcher Affiliations

Nolen-Walston, Rose D
  • Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
Kulp, Jeaneen C
  • Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
Stefanovski, Darko
  • Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
van Eps, Andrew W
  • Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.

MeSH Terms

  • Animals
  • Horses / blood
  • Insulin / blood
  • Immunoenzyme Techniques / veterinary
  • Immunoenzyme Techniques / methods
  • Enzyme-Linked Immunosorbent Assay / veterinary
  • Enzyme-Linked Immunosorbent Assay / methods
  • Reproducibility of Results
  • Female
  • Male
  • Immunoassay / veterinary
  • Immunoassay / methods
  • Horse Diseases / blood
  • Horse Diseases / diagnosis

Grant Funding

  • Laminitis Research Fund, University of Pennsylvania

Conflict of Interest Statement

The authors declare no conflicts of interest.

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