Shortening of an existing generic online health-related quality of life instrument for dogs.

OBJECTIVE: Development, initial validation and reliability testing of a shortened version of a web-based questionnaire instrument to measure generic health-related quality of life in companion dogs, to facilitate smartphone and online use.

MATERIALS AND METHODS: The original 46 items were reduced using expert judgment and factor analysis. Items were removed on the basis of item loadings and communalities on factors identified through factor analysis of responses from owners of healthy and unwell dogs, intrafactor item correlations, readability of items in the UK, USA and Australia and ability of individual items to discriminate between healthy and unwell dogs. Validity was assessed through factor analysis and a field trial using a "known groups" approach. Test-retest reliability was assessed using intraclass correlation coefficients.

RESULTS: The new instrument comprises 22 items, each of which was rated by dog owners using a 7-point Likert scale. Factor analysis revealed a structure with four health-related quality of life domains (energetic/enthusiastic, happy/content, active/comfortable, and calm/relaxed) accounting for 72% of the variability in the data compared with 64% for the original instrument. The field test involving 153 healthy and unwell dogs demonstrated good discriminative properties and high intraclass correlation coefficients.

CLINICAL SIGNIFICANCE: The 22-item shortened form is superior to the original instrument and can be accessed via a mobile phone app. This is likely to increase the acceptability to dog owners as a routine wellness measure in health care packages and as a therapeutic monitoring tool.