BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction

Development of a health-related quality-of-life assessment tool for equines with pituitary pars intermedia dysfunction

BACKGROUND

Clinical signs of pituitary pars intermedia dysfunction (PPID) are frequently mistaken for 'normal' ageing and may not be optimally assessed. Objective quality of life (QoL) assessment could improve clinical decision-making.

OBJECTIVES

To develop an owner-reported health-related quality-of-life (HRQoL) assessment tool for equines with PPID. To assess factors associated with HRQoL scores.

STUDY DESIGN

Quantitative, cross-sectional study.

METHODS

HRQoL tool development followed a standard psychometric process of item (any aspect of PPID and its management that could impact QoL) identification (following interviews with veterinarians, owners and clinical record reviews), selection (online owner questionnaire) and refinement (statistical analyses; chi-squared and Cronbach's alpha). General Linear Models were used to identify factors associated with HRQoL scores.

RESULTS

Forty-two items associated with PPID were identified. Thirty-seven items were selected for the online questionnaire. In total, 612 complete responses (n = 343 PPID and n = 269 non-PPID horses) were obtained. Through stepwise statistical item refinement, 24 items remained in the final HRQoL tool (overall Cronbach's α = 0.835). HRQoL scores ranged from 0 (best) to 1 (worst) QoL. Median (interquartile range) HRQoL scores were 0.33 (0.22-0.44) and 0.20 (0.14-0.27) for PPID and non-PPID horses respectively. HRQoL scores for all horses were worse if they had PPID (p < 0.001) or other chronic medical conditions and were older (p < 0.015). For PPID horses specifically, HRQoL scores were also worse if they had other chronic medical conditions (p = 0.02), but HRQoL scores were not associated with current PPID treatment (treated vs. untreated horses with a PPID diagnosis), bodyweight, age, breed, sex or years since diagnosis.

MAIN LIMITATIONS

Limited numbers of untreated PPID horses.

CONCLUSION

The HRQoL tool is valid and reliable for use in horses with PPID and can be applied in further research. PPID horses with another chronic disease had worse HRQoL scores, which should be considered in other studies evaluating disease impact.

Long-Term Response of Equids With Pituitary Pars Intermedia Dysfunction to Treatment With Pergolide

BACKGROUND

Limited data document long-term responses of equids with pituitary pars intermedia dysfunction (PPID) to pergolide treatment.

OBJECTIVES

Report clinical response, medical problems, outcome, and owner satisfaction with pergolide treatment of PPID-affected equids over 14 years.

ANIMALS

Thirty client-owned equids with PPID.

METHODS

After completion of an open field clinical efficacy study for Prascend® (pergolide tablets), 28 horses and two ponies were enrolled in an extended treatment study (13 receiving 2 μg/kg PO q24h and 17 receiving 4 μg/kg PO q24h). Clients were interviewed every 3 months and equids were re-evaluated after 2.5, 3, 3.5, 4.5, 5.5, 6.5, 9.5, 12.5, and 14.5 years of treatment.

RESULTS

Five equids died and 24 were euthanized (five for chronic laminitis) during the study period (median survival time, 3.6 years; range 0.6-10.5 years). Seven of 13 equids had a dosage increase to 4 μg/kg PO q24h (maximum study dose) between 1.7 to 4.7 years of the study. After 5.5 years, owners of 13 surviving equids reported sustained clinical improvement and endocrine test results normalized in 75%. After 9.5 years of treatment, only two of six surviving equids had normal endocrine test results.

CONCLUSIONS AND CLINICAL IMPORTANCE

Long-term treatment of PPID-affected equids with pergolide produces clinical improvement in nearly all affected animals and normalization of endocrine test results in some cases. Furthermore, this extended treatment study determined that equids can respond favorably long-term to the initial pergolide dose, rather than needing a progressive increase in dose over time.

Association Between Adrenocorticotropic Hormone Concentration and Clinical Signs of Pituitary Pars Intermedia Dysfunction in Swiss and Austrian Equids

BACKGROUND

There remains a scarcity of data concerning the relationship between the clinical signs associated with PPID and plasma ACTH concentrations.

OBJECTIVES

Report the frequency of clinical signs in the study cohort and identify individual clinical signs or combinations of clinical signs associated with high ACTH concentrations.

ANIMALS

Two hundred eighty equids were examined by private veterinarians.

METHODS

A cross-sectional study of animals with clinical suspicion of PPID was conducted between August and November. Private practitioners completed an online questionnaire reporting detailed information, including signalment, owner-reported history, and clinical observations during the examination. Plasma ACTH concentrations of each animal were measured. Associations between clinical signs and ACTH concentrations were examined.

RESULTS

Age, month, and specific clinical signs (hair coat abnormalities, laminitis, and supraorbital fat) were univariably associated with high ACTH concentrations. The first three dimensions of the multiple correspondence analysis (MCA) described the aggregation of clinical signs according to a known semiological typicity. Dimensions 1, 2, and 3 corresponded to features indicative of equine metabolic syndrome, early-stage PPID, and advanced PPID, respectively. Further regression analysis showed that Dimensions 1 and 3, as well as age, were significant predictors of high ACTH levels.

CONCLUSIONS AND CLINICAL IMPORTANCE

The results indicate that particular clinical signs commonly associated with advanced stages of PPID are associated with high ACTH levels. Furthermore, in this data set, a phenotype compatible with metabolic syndrome was also linked to higher ACTH concentrations. These findings underscore the importance of seeking more sensitive biomarkers for the diagnosis of early PPID.

Initial development of a rapid, portable, stall-side ELISA for the measurement of equine adrenocorticotropic hormone

Pituitary pars intermedia dysfunction (PPID) is a neurodegenerative disease of senior horses. Loss of dopaminergic inhibition of the melanotropes of the pars intermedia leads to increased concentrations of pro-opiomelanocortin (POMC)-derived peptides. Diagnosis is challenging due to pre-analytical variables, such as sample storage, handling, and time to analysis. Our objective was to develop an ELISA for ACTH measurement, which could ultimately form the basis for a stall-side equine ACTH test. We selected 2 ACTH-specific monoclonal antibodies, CBL57 and EPR20361-248, based on the recognition of separate epitopes, strong and rapid color change, and minimal background interference, including no cross-reactivity with themselves, each other, and the test reagents. CBL57 was chosen as the detection antibody (or secondary antibody). EPR20361-248, functionalized on superparamagnetic iron oxide beads, was chosen as the capture antibody (or primary antibody) to bind ACTH in plasma. The incorporation of magnetic beads marks the initial stage in establishing a platform that could potentially be utilized in the field, similar to other stall-side tests. The concentrations of antibodies, magnetic beads, and incubation durations were optimized. Our immunoassay detected unglycosylated rat recombinant ACTH. Further studies are ongoing to optimize and validate our assay using equine plasma and serum samples.

Factors affecting measurement of basal adrenocorticotropic hormone in adult domestic equids: A scoping review

Measurement of basal adrenocorticotropic hormone (ACTH) concentration is the most commonly used diagnostic test for pituitary pars intermedia dysfunction (PPID). Although several pre-analytical and analytical factors have been reported to affect basal ACTH concentrations in equids, the extent to which these have been evaluated in the context of PPID diagnosis is unclear. The objectives of this scoping review were to identify and systematically chart current evidence about pre-analytical and analytical factors affecting basal ACTH concentrations in adult domestic equids. Systematic searches of electronic databases and conference proceedings were undertaken in June 2022, repeated in October 2022 and updated in August 2023. English language publications published prior to these dates were included. Screening and data extraction were undertaken individually by the authors, using predefined criteria and a modified scoping review data extraction template. After removal of duplicates, 903 publications were identified, of which 235 abstracts were screened for eligibility and 134 publications met inclusion criteria. Time of year, exercise, breed/type and transportation were the factors most frequently associated with significant increases in ACTH concentration (n = 26, 16, 13 and 10 publications, respectively). Only 25 publications reported inclusion of PPID cases in the study population, therefore the relationship between many factors affecting basal ACTH concentration and diagnostic accuracy for PPID remains undefined. However, several factors were identified that could impact interpretation of basal ACTH results. Findings also highlight the need for detailed reporting of pre-analytical and analytical conditions in future research to facilitate translation of evidence to practice.