Objective measurement of pruritus in dogs: a preliminary study using activity monitors

Pruritus is an important clinical sign and quality-of-life measure in canine dermatology, but can be difficult to assess objectively. Several studies in humans have used activity monitors to measure nocturnal scratching in patients with atopic dermatitis. The results correlate with observation of scratching, scoring in atopic dermatitis indices and levels of inflammatory chemokines. The aim of this study was to examine whether an activity monitor could be used to detect elevated interexercise (i.e. 'resting') activity in atopic dogs compared to healthy dogs. Five healthy dogs and six dogs with atopic dermatitis were fitted with a collar-mounted activity monitor (Actiwatch) that recorded the piezo-electric voltage generated over 15-s epochs for 7 days. Data from defined periods of exercise, playing, etc., were disregarded. Within each group, median (+/- interquartile range) epoch activity was similar during the day (atopic 21.0 [9.8-24.8]; healthy 5.1 [4.6-6.0]) and evening (atopic 19.1 [10.9-25.2]; healthy 5.8 [5.3-11.7]), and significantly lower overnight (atopic 5.8 [4.1-15.7]; healthy 2.5 [1.6-4.4]) (Mann-Whitney test; P < 0.05). The mean epoch activity, however, was significantly higher in atopic dogs compared to healthy dogs for all three time periods (P < 0.05). This study provides preliminary evidence that activity monitors could objectively assess canine pruritus in the normal home environment.