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Equine veterinary journal2020; 52(5); 709-714; doi: 10.1111/evj.13227

Comparison of immunofluorescence and chemiluminescence assays for measuring ACTH in equine plasma.

Abstract: The chemiluminescence (CL) and immunofluorescence (IF) assays yield different results for basal adrenocorticotropin hormone concentrations [ACTH] in pony plasma. It is unclear whether this difference also occurs in basal samples from horses or samples from ponies following thyrotropin-releasing hormone (TRH) stimulation. Objective: To compare the results of [ACTH] analysis by CL and IF methods in basal samples from horses and pony samples following TRH stimulation. Methods: Method comparison. Methods: Plasma [ACTH] was measured concurrently using CL and IF methods in 12 ponies (basal and post-TRH stimulation) in November and basal samples from horses (n = 45; November and May). Results: CL and IF methods yielded different results (P < .01). The median difference (CL-IF) (95% CI) for ponies was 5.9 (0.1-7.5) pg/mL at baseline and 227.9 (61-1001) pg/mL post TRH; and horses 1.9 (1.1-5.4) pg/mL in November and 9.4 (8.2-11.5) pg/mL in May, at baseline. Correlation was good in ponies at baseline (R = 0.80, P = .003) but not post-TRH, and good in horses in November and May (R = 0.68 and 0.71, P 29 and >110 pg/mL, agreement was moderate (ƙ = 0.67) and very good (ƙ = 0.82) for binary classification of PPID in ponies at baseline and post-TRH; and good (ƙ = 0.73) for horses in November, but poor (ƙ = 0.40) in May. Conclusions: Limited numbers of horses with [ACTH] above threshold values. Conclusions: The assays yielded different absolute values, particularly in post-TRH samples from ponies, suggesting TRH stimulates secretion of cross-reacting peptides other than ACTH. Agreement for binary classification for PPID was moderate to good, except in basal samples from horses in May.
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Publication Date: 2020-02-18 PubMed ID: 31955443DOI: 10.1111/evj.13227Google Scholar: Lookup
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Summary

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The research article investigates the differences between chemiluminescence (CL) and immunofluorescence (IF) assays in measuring Adrenocorticotropin Hormone (ACTH) in horse and pony plasma. The findings indicate significant discrepancies between the two methods, particularly after thyrotropin-releasing hormone (TRH) stimulation in ponies.

Research Methodology

  • This study compared the results of ACTH analysis using CL and IF methods.
  • Plasma ACTH levels were measured in 12 ponies, both at a basal level and following TRH stimulation, and in 45 horses’ basal samples.
  • These measurements took place in November and May for the horses, providing a seasonal comparison.

Results and Observations

  • The results showed that the CL and IF methods yielded different results, with statistical significance (P < .01).
  • For ponies, the median difference was 5.9 pg/mL at baseline and 227.9 pg/mL post TRH stimulation.
  • Additionally, for horses, the median difference was 1.9 pg/mL in November and 9.4 pg/mL in May at baseline.
  • These differences suggest that the TRH stimulation prompts the secretion of peptides that cross-react with ACTH.
  • Despite the discrepancy in absolute values, the correlation was good in ponies at baseline and in horses in November and May.
  • Bland-Altman analysis showed moderate bias and wide limits of agreement in the baseline data and large bias and wide limits in the post-TRH pony data.

Conclusions

  • Although there is a noticeable difference in the absolute values produced by the two assays, especially in the post-TRH samples sourced from ponies, the agreement for binary classification of Pituitary Pars Intermedia Dysfunction (PPID) was generally good.
  • The exception was for basal samples from horses in May, which showed poor agreement.
  • It’s suggested that the inconsistency between CL and IF assays may be due to TRH stimulation provoking the secretion of cross-reacting peptides that aren’t ACTH.
  • However, the study included a limited number of horses with ACTH above threshold values, which could affect the conclusions.

Cite This Article

APA
McGilvray TA, Knowles EJ, Harris PA, Menzies-Gow NJ. (2020). Comparison of immunofluorescence and chemiluminescence assays for measuring ACTH in equine plasma. Equine Vet J, 52(5), 709-714. https://doi.org/10.1111/evj.13227

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 52
Issue: 5
Pages: 709-714

Researcher Affiliations

McGilvray, Tegan A
  • The Royal Veterinary College, North Mymms, Hatfield, Hertfordshire, UK.
Knowles, Edward J
  • The Bell Equine Veterinary Clinic, Mereworth, Kent, UK.
Harris, Pat A
  • WALTHAM Centre for Pet Nutrition, Leicestershire, UK.
Menzies-Gow, Nicola J
  • The Royal Veterinary College, North Mymms, Hatfield, Hertfordshire, UK.

MeSH Terms

  • Adrenocorticotropic Hormone
  • Animals
  • Fluorescent Antibody Technique / veterinary
  • Horse Diseases
  • Horses
  • Luminescence
  • Luminescent Measurements / veterinary
  • Thyrotropin-Releasing Hormone

Grant Funding

  • MARS Petcare UK

References

This article includes 16 references
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Citations

This article has been cited 4 times.
  1. Drozdzewska K, Gehlen H. Markers for internal neoplasia in the horse. Vet Med Sci 2023 Jan;9(1):132-143.
    doi: 10.1002/vms3.1042pubmed: 36495211google scholar: lookup
  2. Hinrichsen SL, Yuen KY, Dryburgh EL, Bertin FR, Stewart AJ. Short-Term Effects of Temperature and Thyrotropin-Releasing Hormone Stimulation on Adrenocorticotropin Stability in Horses. Animals (Basel) 2022 Jan 28;12(3).
    doi: 10.3390/ani12030324pubmed: 35158648google scholar: lookup
  3. Thane K, Uricchio C, Frank N. Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses. J Vet Intern Med 2022 Mar;36(2):770-777.
    doi: 10.1111/jvim.16362pubmed: 35049089google scholar: lookup
  4. Vaughn SA, Lemons MB, Hart KA. The Effect of Season and Breed on Hypothalamic-Pituitary-Adrenal Axis Hormones, Metabolic Hormones, and Oxidative Markers in Ponies and Horses. J Vet Intern Med 2025 Mar-Apr;39(2):e70047.
    doi: 10.1111/jvim.70047pubmed: 40048369google scholar: lookup
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