Plasma adrenocorticotropic hormone (ACTH) concentrations in ponies measured by two different assays suggests seasonal cross‐reactivity or interference

Knowles, E. J.; Moreton-Clack, Michelle; Shaw, S.; Harris, Pat; Elliott, Jonathan; Menzies‐Gow, N. J.

doi:10.1111/evj.12797

Cited by 21 publications

(30 citation statements)

References 17 publications

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“…Durham, unpublished data). It is also worthy of note that other methodologies might not generate values that vary in any predictably linear fashion meaning that extrapolation may prove impossible 31,32 …”

Section: Discussionmentioning

confidence: 99%

Clinically and temporally specific diagnostic thresholds for plasma ACTH in the horse

Durham¹,

Clarke

Potier³

et al. 2020

Equine Veterinary Journal

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Background Pituitary pars intermedia dysfunction (PPID) is commonly investigated using plasma ACTH concentrations but problems exist with currently available diagnostic thresholds. Objectives To derive temporally specific diagnostic thresholds for equine plasma ACTH concentration to be used alongside clinical judgement in each individual week of the year and appropriate for the degree of clinical suspicion in any given case. Furthermore, to apply these thresholds to compare the prevalence of high and low ACTH in two subgroups of animals with high and low clinical suspicion of PPID. Study design A retrospective population study examining a large laboratory database of equine plasma ACTH concentrations using an indirect approach to calculate diagnostic thresholds. Methods Logs of plasma ACTH concentrations from 75 892 individual horses were examined using robust L2 estimation of mixtures of two normal distributions in categories of each week and month of the year. Thresholds dividing the two populations of high‐ACTH and low‐ACTH horses were then established at different levels of sensitivity and specificity and compared with clinical subgroups of horses divided based on reported clinical signs, as having high (n = 4036) or low (n = 3022) clinical suspicion of PPID. Results For most of the year there were small interweek differences in diagnostic thresholds. However, from mid‐June to early‐December diagnostic thresholds showed greater interweek variability, reaching a maximum in late September and early October. Grouping of high‐ and low‐ACTH compared favourably with grouping based on clinical signs. Main limitations Given the multiple sources of diagnostic samples, pre‐analytical data could not be fully verified. Conclusions Diagnostic thresholds for equine plasma ACTH vary through the year. It is especially important to consider the temporally specific threshold between June and December. Different clinical thresholds can be used depending on the case circumstances and whether a false‐positive or false‐negative diagnosis is deemed least desirable.

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Section: Discussionmentioning

confidence: 99%

Clinically and temporally specific diagnostic thresholds for plasma ACTH in the horse

Durham¹,

Clarke

Potier³

et al. 2020

Equine Veterinary Journal

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show abstract

“…Analytic measurement techniques, especially in autumn months, have been shown to influence ACTH results, due to cross‐reaction with other plasma pituitary peptides . Tests in this study were performed in summer months and ACTH concentrations were measured using a valid method for all samples (chemiluminescent immunoassay) including samples measured at Cornell's laboratory, making these factors unlikely to have influenced the results.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of dynamic testing for pituitary pars intermedia dysfunction diagnosis in donkeys

Mejia‐Pereira¹,

Pérez-Écija

Buchanan³

et al. 2018

Equine Veterinary Journal

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Summary Background Endocrine disorders are common in donkeys. Pituitary pars intermedia dysfunction (PPID) is thought to be a frequent disturbance in donkeys due to their longevity. However, information on PPID dynamic testing in donkeys is lacking. Objectives The objective of this study was to evaluate the previously described guidelines for PPID diagnosis in horses in donkeys with suspicion of PPID. Study design Prospective experimental study. Methods Eighty donkeys were evaluated for PPID suspicion based on clinical signs and baseline adrenocorticotropic hormone (ACTH) concentrations. Six mix‐breed donkeys (one jack and five non‐pregnant jennies) fulfilling inclusion criteria were subjected to dexamethasone suppression test (DST), thyrotropin‐releasing hormone stimulation test (TRH) and combined DST–TRH challenge. Tests were interpreted according to guidelines for PPID diagnosis in horses. Results Donkeys fulfilling inclusion criteria were diagnosed with PPID by TRH stimulation test (six of six). Both DST (three of six) and DST–TRH (4/6) challenges failed to detect those animals and showed conflicting results. Similarly, cortisol basal concentrations were not consistent with PPID suspicion. Main limitations Characterisation of seasonal and geographical location effect on baseline ACTH concentrations and response to TRH is compelling in this species. Further studies with a larger number of donkeys are needed. Conclusions This is the first study in donkeys to evaluate common dynamic tests used for PPID diagnosis in horses. Preliminary results agree with the guidelines for PPID diagnosis in horses and baseline ACTH measurement followed by TRH challenge are recommended tests for diagnosis of PPID in donkeys.

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“…In contrast, in clinically normal horses the majority of ACTH measured in the plasma originates from the PD, as ACTH from the PI is cleaved into other POMC‐derived peptides and does not reach the systemic circulation . The effect of the circannual cycle on plasma endogenous ACTH in clinically normal horses, when measured by commercially available assays, may be caused by cross‐reactivity or interference with other POMC‐derived peptides that are produced in greater concentrations during certain times of the circannual cycle, rather than by increased production of ACTH from the PD …”

Section: Diagnosismentioning

confidence: 99%

Equine pituitary pars intermedia dysfunction: current understanding and recommendations from the Australian and New Zealand Equine Endocrine Group

et al. 2018

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The purpose of this article is to provide a review of the current knowledge and opinions about the epidemiology, clinical findings (including sequelae), diagnosis, treatment and monitoring of equine pituitary pars intermedia dysfunction, particularly in the Australian context. This information and the recommendations provided will assist practitioners in making informed decisions regarding the diagnosis and management of this disorder.

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Plasma adrenocorticotropic hormone (ACTH) concentrations in ponies measured by two different assays suggests seasonal cross‐reactivity or interference

Abstract: The methods yielded different absolute values but the agreement for binary classification was good. An altered pituitary secretome in autumn that affects apparent [ACTH] values is likely. The Summary is available in Spanish - see Supporting information.

Cited by 21 publications

References 17 publications

Clinically and temporally specific diagnostic thresholds for plasma ACTH in the horse

Clinically and temporally specific diagnostic thresholds for plasma ACTH in the horse

Evaluation of dynamic testing for pituitary pars intermedia dysfunction diagnosis in donkeys

Equine pituitary pars intermedia dysfunction: current understanding and recommendations from the Australian and New Zealand Equine Endocrine Group

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