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Home / Equine Research Bank / J Vet Intern Med / Effect of early or late blood sampling on thyrotropin releas...
Journal of veterinary internal medicine2022; 36(2); 770-777; doi: 10.1111/jvim.16362

Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses.

Abstract: Diagnosis of pituitary pars intermedia dysfunction (PPID) using the thyrotropin-releasing hormone (TRH) stimulation test requires blood collection 10 minutes after TRH injection; it is unknown if small differences in timing affect test results. Objective: To determine whether early or late sampling results in a significant (≥10%) difference in plasma adrenocorticotropic hormone (ACTH) concentration compared to standard 10-minute sampling. Methods: Twenty-four healthy adult horses with unknown PPID status. Methods: In this prospective study, subjects underwent a single TRH stimulation test, with blood collected exactly 9 minutes (early), 10 minutes (standard), and 11 minutes (late) after injection. ACTH was measured by chemiluminescent immunoassay. Two aliquots of the 10-minute plasma sample were analyzed separately to assess intra-assay variability. Data were reported descriptively and bias was calculated using Bland-Altman plots. Significance was set at P = .05. Results: Minor variability was observed between the paired 10-minute sample aliquots (range, 0%-6%; median 3%). Overall variability of early or late samples compared to the corresponding paired (average) 10-minute standard concentration ranged from 0% to 92% (median 10%). Seventy-five percent of horses (18/24) tested had at least 1 early or late reading that differed by ≥10% from its corresponding 10-minute standard concentration, and 21% of horses (5/24) would have a different interpretation of testing result with either early or late sampling. Incidence of ≥10% variability was independent of PPID status (P = .59). Conclusions: Precise timing of sample collection is critical to ensure accurate assessment of PPID status given the observation of significant variability associated with minor alterations in timing of sample collection.
© 2022 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC. on behalf of the American College of Veterinary Internal Medicine.
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Publication Date: 2022-01-20 PubMed ID: 35049089PubMed Central: PMC8965261DOI: 10.1111/jvim.16362Google Scholar: Lookup
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  • Journal Article

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 studied the impact of small timing differences in blood sampling during thyrotropin-releasing hormone (TRH) stimulation test on the diagnosis of pituitary pars intermedia dysfunction (PPID) in horses. The findings suggest that precision in blood sampling timing is essential since minor departures from standard timing can significantly influence the plasma adrenocorticotropic hormone (ACTH) concentration and thus, interpretation of test results.

Objective and Methodology

  • The researchers aimed to ascertain if early or late blood sampling led to significant differences (≥10%) in plasma ACTH concentration compared to the 10-minute standard blood collection after TRH injection which is a clinical norm for diagnosing PPID in horses.
  • Twenty-four healthy adult horses of unknown PPID status were included in this study. They underwent a single TRH stimulation test where blood was collected exactly at 9 minutes (early), 10 minutes (standard), and 11 minutes (late) after the TRH injection. The ACTH levels in the blood were then measured using chemiluminescent immunoassay.
  • This prospective study also analyzed two aliquots of the 10-minute plasma sample separately to determine intra-assay variability. The data bias was addressed using statistical methods with set significance at P = .05.

Results

  • The research observed minor variability (0%-6%, median 3%) between the paired 10-minute sample aliquots, showing reliable intra-assay consistency.
  • The variability in early or late samples compared to the standard 10-minute blood sample ranged from 0% to 92% (median 10%). It implies that minor changes in the timing of blood collection could lead to high variability in ACTH concentration measured.
  • Out of the horses tested, 75% had at least one early or late reading differing by ≥10% from its corresponding 10-minute standard concentration. It would significantly alter the interpretation of test results in 21% of horses.
  • The researchers concluded that ≥10% variability was independent of the horse’s PPID status since the statistical correlation was insignificant (P = .59).

Conclusion

  • The research concluded that precise timing of blood sample collection is crucial for an accurate assessment of PPID status in horses.
  • Even minor alterations in the timing of sample collection led to significant variability in ACTH concentration, thereby possibly affecting the test result interpretation and diagnostic accuracy for PPID.

Cite This Article

APA
Thane K, Uricchio C, Frank N. (2022). Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses. J Vet Intern Med, 36(2), 770-777. https://doi.org/10.1111/jvim.16362

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 36
Issue: 2
Pages: 770-777

Researcher Affiliations

Thane, Kristen
  • Tufts Cummings School of Veterinary Medicine, Department of Comparative Pathobiology, North Grafton, Massachusetts, USA.
Uricchio, Cassandra
  • University of Massachusetts, Department of Veterinary and Animal Sciences, Amherst, Massachusetts, USA.
Frank, Nicholas
  • Tufts Cummings School of Veterinary Medicine, Department of Comparative Pathobiology, North Grafton, Massachusetts, USA.

MeSH Terms

  • Animals
  • Horse Diseases
  • Horses
  • Pituitary Diseases / diagnosis
  • Pituitary Diseases / veterinary
  • Pituitary Gland, Intermediate
  • Prospective Studies
  • Thyrotropin-Releasing Hormone

Grant Funding

  • PR0481 / Boehringer Ingelheim Vetmedica, Inc

Conflict of Interest Statement

Dr Frank consults on study design and the diagnosis and treatment of pituitary pars intermedia dysfunction in horses for Boehringer Ingelheim, which provided funds to support this study.

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Citations

This article has been cited 2 times.
  1. Kirkwood NC, Hughes KJ, Stewart AJ. Prospective Case Series of Clinical Signs and Adrenocorticotrophin (ACTH) Concentrations in Seven Horses Transitioning to Pituitary Pars Intermedia Dysfunction (PPID).. Vet Sci 2022 Oct 17;9(10).
    doi: 10.3390/vetsci9100572pubmed: 36288186google scholar: lookup
  2. Kirkwood NC, Hughes KJ, Stewart AJ. Pituitary Pars Intermedia Dysfunction (PPID) in Horses.. Vet Sci 2022 Oct 10;9(10).
    doi: 10.3390/vetsci9100556pubmed: 36288169google scholar: lookup
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