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.

Measurement of basal adrenocorticotrophic hormone (ACTH) is currently used to diagnose pituitary pars intermedia dysfunction (PPID) in horses, yet a systematic review of the evidence for its use has not been undertaken. This study aimed to systematically review evidence regarding the sensitivity and specificity of the basal ACTH diagnostic test. Electronic databases were systematically searched in January 2019, September 2020 and January 2021, for English language publications published prior to these dates. Screening, data extraction and quality assessment of publications was undertaken by the authors using predefined criteria. Study design, methodology and information reported in included studies were assessed using Standards for Reporting of Diagnostic Accuracy (STARD) checklists. Risk of bias and applicability were appraised using the Quality Assessment tool for Diagnostic Accuracy Studies (QUADAS-2) quality assessment tool. Due to identified biases and marked between-study variations, meta-analysis was not undertaken. After removal of duplicates, 415 publications were identified, of which 25 were evaluated in full, with 11 of these meeting inclusion criteria. In most studies, basal ACTH was reported to have good sensitivity (overall median 75.5%; interquartile range [IQR], 64.0-86.5%; range, 36.0-100%) and excellent specificity (overall median, 95.2%; IQR, 84.2-98.9%; range, 63.3-100%). However, QUADAS-2 and STARD assessment highlighted that studies did not utilise optimal study design and/or study populations for the evaluation of a diagnostic test and the majority were subject to bias, or provided insufficient information to fully assess possible biases. Based on this review, basal ACTH performed better at ruling out PPID than detecting it.

Pergolide, a dopamine agonist, is commonly administered to manage pituitary pars intermedia dysfunction (PPID), a progressive neurodegenerative disease prevalent in aged horses. However, available evidence regarding pergolide\'s efficacy in improving clinical and endocrine parameters is limited. The aim of this systematic review was to assess published literature and evaluate evidence regarding whether pergolide treatment results in improvement of clinical signs and/or adrenocorticotrophic hormone (ACTH) concentration compared to no treatment or other unlicensed treatments. Systematic searches of electronic databases were undertaken in April 2019, repeated in August and October 2019, and updated in July 2020. English language publications published prior to these dates were included. Screening, data extraction and quality assessment of publications was undertaken individually by the authors using predefined criteria and subsequently cross-checked. Modified critically appraised topic data collection forms were used to extract data. Due to marked between-study variations, meta-analysis was not undertaken. After removal of duplicate records; 612 publications were identified, of which 129 abstracts were screened for eligibility and 28 publications met criteria for inclusion in the review. Most studies were descriptive case series, cohort studies or non-randomised, uncontrolled field trials. Despite marked variation in study populations, case selection, diagnostic protocols, pergolide dose, follow-up period and outcome measures, in the vast majority of the included studies, pergolide was reported to provide overall clinical improvement in >75% of cases. However, reported improvements in individual clinical signs varied widely. A reduction in plasma ACTH concentrations was reported in 44-74% of cases, while normalisation to within reported reference intervals occurred in 28-74% of cases.

Pituitary pars intermedia dysfunction (PPID) is caused by an age-related degenerative disease of dopaminergic neurones. Despite its importance in equine practice, available information regarding its epidemiology is limited. This systematic review aimed to assess published literature to evaluate available evidence regarding the clinical presentation, prevalence and risk factors for PPID in horses and ponies. Electronic database searches were undertaken using a range of terms, and English language publications published prior to August 2016 were included. Both authors independently reviewed screened papers for inclusion, extracted data, and assessed the quality of reporting using predefined criteria. Data were extracted using modified critically appraised topic data collection forms. Meta-analysis was not undertaken due to marked between-study variations. Following removal of duplicate records, of 358 published papers yielded by the search, 97 abstracts were screened for eligibility and 29 publications meeting inclusion criteria were included in the review. Most studies reviewed were case series or cross-sectional studies, with considerable variation in study populations and PPID case definition. Hypertrichosis and/or other hair coat abnormalities, laminitis and epaxial muscle wastage or muscle atrophy are the most frequently reported clinical signs, with prevalence of these signs increasing with increasing horse age. The most robust prevalence estimates for PPID were 21.2% in horses and ponies aged ≥15 years and 2.9% amongst the general equine population. Findings regarding breed and sex predispositions were equivocal and only increasing age has been identified as a significant risk factor for PPID.