Factors affecting measurement of basal adrenocorticotropic hormone in adult domestic equids: A scoping review.
Authors: Ireland J L, Lester A, Banse H E
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Basal ACTH measurement remains the primary diagnostic tool for equine pituitary pars intermedia dysfunction (PPID), yet the reliability of this test is compromised by numerous variables that can elevate hormone concentrations independently of disease. Ireland and colleagues conducted a comprehensive scoping review of 134 peer-reviewed publications to systematically identify pre-analytical and analytical factors influencing basal ACTH measurements in adult horses and donkeys. Seasonal variation, exercise, breed predisposition, and transportation stress emerged as the factors most frequently reported to significantly increase ACTH concentrations, identified across 26, 16, 13 and 10 studies respectively; however, the clinical significance of these findings for PPID diagnosis remains poorly defined because only 25 of the included publications actually studied affected animals. The authors highlight a critical evidence gap: whilst we know these factors alter basal ACTH, we lack clarity on how they influence diagnostic accuracy in animals with confirmed PPID versus healthy controls, meaning practitioners cannot reliably contextualise borderline or elevated results. Their recommendation for standardised reporting of pre-analytical and analytical conditions in future research underscores an urgent need to refine testing protocols—ensuring that PPID diagnoses rest on robust interpretation rather than assumption.
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Practical Takeaways
- •When interpreting basal ACTH results for PPID diagnosis, consider that seasonal variation, recent exercise, breed differences, and transportation stress can all elevate concentrations independent of disease
- •Request detailed information about sampling conditions and timing from your laboratory, as standardized pre-analytical protocols are inconsistently reported across testing facilities
- •Be cautious about single basal ACTH measurements; the numerous factors affecting this test suggest serial sampling or additional diagnostic tests (e.g., TRH stimulation) may improve diagnostic confidence
Key Findings
- •Time of year, exercise, breed/type, and transportation were the most frequently reported factors significantly affecting basal ACTH concentrations (26, 16, 13, and 10 publications respectively)
- •Only 25 of 134 included publications reported PPID cases in their study population, leaving the relationship between many ACTH-affecting factors and diagnostic accuracy undefined
- •Multiple pre-analytical and analytical factors were identified that could impact interpretation of basal ACTH results, but their clinical significance for PPID diagnosis remains unclear