Background
Transepidermal water loss (TEWL) and surface capacitance measure skin barrier permeability and stratum corneum (SC) hydration, respectively, and are frequently utilized in atopic dermatitis clinical trials. Many barrier devices are costly and often used only in the academic setting. GPSkin is a low‐cost, patient‐operated device that measures both TEWL and SC hydration. This study aimed to test the reliability of GPSkin and assess its correlation with current industry standards.
Materials and Methods
GPSkin was compared to the Biox AquaFlux (TEWL) and Courage‐Khazaka Corneometer (SC hydration). Participants with healthy skin (n = 50) collected measurements with GPSkin in Trial 1 without any device education and in Trial 2 with additional instruction. In Trial 2, the investigator also performed measurements with GPSkin. Spearman's coefficients (rs) were performed to assess device correlation. Intraclass correlation coefficients (ICC) were calculated to determine reliability.
Results
Overall, GPSkin was moderately correlated with current industry device measurements for TEWL (Trial 1 rs:0.48; Trial 2 rs:0.40 participant, 0.34 investigator) and SC hydration (Trial 1 rs:0.63; Trial 2 rs:0.45). GPSkin demonstrated “good” test‐retest reliability for both TEWL (ICC: 0.89) and SC hydration (ICC: 0.85) measurements when participants were provided with some device education. There was no difference in reliability between participants provided with device education and investigators.
Conclusion
Based on these findings, we concluded that GPSkin provides reasonably precise and reliable measurements of SC hydration and TEWL as compared to current devices.
and T.B. were involved in development of the RECAP instrument. A.G., L.E. and E.S. were involved in development of the ADCT instrument. A.G. and L.E. were involved in development of the peak NRS-11 itch instrument. M.B. was our independent chair and had no conflicts of interest.
Atopic dermatitis is a chronic inflammatory skin condition that affects approximately 18 million people in the United States. Assessing the extent and severity of atopic dermatitis is critical for determining baseline disease burden and treatment effectiveness for both investigators and clinicians. Considerable efforts over the past several decades have been made in developing a highly validated instrument called the Eczema Area and Severity Index (EASI). Although several guides exist for the EASI, questions continue to arise regarding its use and interpretation. This review was developed to serve as the definitive guide for the EASI and to address commonly asked questions.
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