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

Abstract

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.