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Equine veterinary journal2023; doi: 10.1111/evj.13991

Clinical implications of imprecise sampling time for 10- and 30-min thyrotropin-releasing hormone stimulation tests in horses.

Abstract: The thyrotropin-releasing hormone (TRH) stimulation test is used to diagnose pituitary pars intermedia dysfunction (PPID) using 10- or 30-min protocols. Imprecise sampling time for the 10-min protocol can lead to misdiagnoses. Objective: To determine the effect of imprecise sampling time for the 30-min protocol of the TRH stimulation test. Methods: In vivo experiment. Methods: Plasma immunoreactive adrenocorticotropin (ACTH) concentrations were measured 9, 10, 11, 29, 30 and 31 min after intravenous administration of 1 mg of TRH in 15 control and 12 PPID horses. Differences in ACTH concentrations between sampling times, variability in ACTH concentrations between protocols, and diagnostic classification of PPID were assessed using Friedman's test, Bland-Altman plots, and Fisher's exact test, respectively, with 95% confidence intervals reported and significance set at p < 0.05. Results: Imprecise sampling time resulted in variable ACTH concentrations, but significant differences in absolute ACTH concentrations were not detected for imprecise sampling within each protocol or between protocols. Imprecise sampling changed PPID diagnostic classification for 3/27 (11 [4-28] %) horses for both protocols. Using the 30-min protocol as a reference, 1/12 (8 [1-35] %) horses returned a negative test result and 5/12 (42 [19-68] %) horses returned equivocal test results that would be considered positive in practice due to the presence of supportive clinical signs. Conclusions: Limited sample size and inter-horse variability reduced the ability to detect small but potentially relevant differences. Conclusions: Overall, the impact of imprecise sampling was not significantly different between the 10- and 30-min TRH stimulation test protocols. However, diagnostic classification for PPID would have varied between the 10- and 30-min protocols in this population, if clinical signs had been ignored. Precise timing during TRH stimulation tests and contextual interpretation of ACTH concentrations remain fundamental for the diagnosis of PPID.
© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2023-08-30 PubMed ID: 37649416DOI: 10.1111/evj.13991Google Scholar: Lookup
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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.

This research examined the effect of slight timing errors in blood sampling after the administration of thyrotropin-releasing hormone (TRH) in tests used to diagnose a pituitary disorder in horses. The findings showed that these timing errors did not significantly affect the results between the 10-minute and 30-minute protocols, although the accuracy of the diagnosis might vary if clinical signs were disregarded.

Methodology

  • The researchers conducted an in vivo experiment on 15 control horses and 12 horses with pituitary pars intermedia dysfunction (PPID).
  • They intravenously administered 1mg of TRH and subsequently measured plasma adrenocorticotropin (ACTH) concentrations at 9, 10, 11, 29, 30, and 31 minutes post-administration.
  • This accuracy of these measurements was then assessed using statistical methods like Friedman’s test, Bland-Altman plots, and Fisher’s exact test. The threshold for statistical significance was set at p < 0.05.

Findings

  • Inconsistent sampling times led to variable ACTH concentrations, but these didn’t result in significant differences within or between protocols.
  • However, such inconsistencies did affect the PPID diagnostic classification for 11% of horses in both protocols.
  • Using the 30-minute protocol as a reference, one horse returned a negative result and five horses came back with ambiguous results—though, these would normally be considered positive due to visible clinical signs.

Limitations and Conclusion

  • The researchers indicated that the limited sample size and variability between horses may have hindered the detection of small but potentially relevant differences.
  • While they concluded that the overall impact of imprecise sampling wasn’t significantly different between the 10- and 30-minute TRH stimulation tests, the diagnostic classification for PPID could differ if clinical signs were dismissed.
  • They emphasized the importance of precise timing during TRH stimulation tests and the context-based interpretation of ACTH concentrations for accurate PPID diagnosis.

Cite This Article

APA
Vorster DM, Wang W, Kemp KL, Bamford NJ, Bertin FR. (2023). Clinical implications of imprecise sampling time for 10- and 30-min thyrotropin-releasing hormone stimulation tests in horses. Equine Vet J. https://doi.org/10.1111/evj.13991

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Vorster, Dante M
  • Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
Wang, Wenqing
  • School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Kemp, Kate L
  • School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Bamford, Nicholas J
  • Melbourne Veterinary School, The University of Melbourne, Parkville, Victoria, Australia.
Bertin, François-René
  • School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.

Grant Funding

  • Australian Companion Animal Health Foundation

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This article includes 32 references
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Citations

This article has been cited 1 times.
  1. Wang W, Gibson J, Horsman S, Mikkelsen D, Bertin FR. Characterization and comparison of fecal microbiota in horses with pituitary pars intermedia dysfunction and age-matched controls. J Vet Intern Med 2025 Jan-Feb;39(1):e17288.
    doi: 10.1111/jvim.17288pubmed: 39853825google scholar: lookup
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