Objective evaluation of scratching action using an artificial nail apparatus

Abstract

The purposes of this study were to measure behaviors associated with scratching via an artificial nail apparatus and to objectively evaluate itch severity. Four healthy volunteers (three men and one woman) were recruited and wore an artificial nail apparatus on each fingertip, excluding the thumb. The participants scratched four parts of their body (forearm, thigh, upper arm, and head) in a usual manner, and signals generated by the sensors in the apparatus were recorded. The amplitude, frequency, and integrated values over 10-s durations from each scratching waveform were validated. Each parameter was statistically analyzed using one-way analysis of variance multiple comparison tests and the Mann-Whitney U test for comparisons among fingers, scratch strength, scratch areas, and between bare and clothed skin. Among the four fingers, the amplitude and integrated values were higher for the index and middle fingers than for the ring and little fingers. The scratching frequency was higher, and the total amplitude tended to be lower in the head area compared to other parts of the body. The scratch strength was well correlated with the amplitude. All values for scratching clothed skin were higher than those for scratching bare skin (p<0.05). Our artificial nail apparatus is useful for objectively evaluating scratching action and itch severity.