Objective: Deterioration of the skin’s barrier function increases the risk of skin problems. Accurate and quantitative measurement of skin hydration is necessary for the assessment of skin. Here, we aimed to evaluate the reliability and validity of a portable device for measuring stratum corneum hydration.
Methods: This was a quasi-experimental study. Participants included 37 healthy volunteers and 3 raters. For the assessment of intra-rater, inter-rater, and inter-device reliability, the volar forearm was measured three times consecutively by a rater using two portable devices. The same procedure was then performed by two other raters. For concurrent and known-groups validity testing, measurements were taken of the forehead, volar forearm, and heel using the portable device and a standard device. The study protocol was approved by an ethics committee.
Results: The intra-class correlation coefficients(ICCs)were 0.97-0.99 for intra-rater reliability, 0.88-0.96 for inter-rater reliability, and 0.89-0.94 for inter-device reliability. Spearman’s rank correlation coefficients between measurements obtained using the portable device and the standard device demonstrated concurrent validity: 0.92(p < 0.001)for the volar forearm, 0.82(p < 0.001)for the forehead, and 0.80(p < 0.001)for the heel. The stratum corneum hydration of the heel was significantly lower than that of the forearm when measured using the portable device or the standard device(p < 0.001 for both devices), supporting the known-groups validity of portable device.
Conclusion: The portable device demonstrated sufficient reliability and validity for use in clinical and research settings.
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