Supplementary Material for: Stratum corneum hydration measurements with a Bluetooth wireless probe: A real life study at home compared to measurements under laboratory conditions

Introduction and aims: Non-invasive measurement of the stratum corneum hydration (SCH) with capacitance-based instrumentation is established in dermatological and cosmetic studies. We wanted to test the reliability of non-invasive self-measurements for SCH performed under real-life conditions by volunteers with a Bluetooth-based (wireless) probe Corneometer® (CM825i) transmitting the data via a smartphone application to a central server. Probes and smartphones communicated using Bluetooth Low Energy (BLE). Data from the smartphone was securely transferred to a remote server in a different country with TLS encryption using HTTPS protocols. CM825i values were correlated with the established CM825 under laboratory conditions. The primary endpoint was the correlation of the two probes. Secondary endpoints were the coefficient of variation (CV) and delta values (before and after treatment). Material and methods: 18 healthy volunteers (f:8; m:10) participated in the prospective observational study. The real-world home use of the wireless CM825i was performed before and after treatments with base cream-DAC for 7 days. Results: Both instruments showed a significant and relevant correlation (p<0.0001; Spearman coefficient r=0.8647). CM825i and CM825 differentiate significantly between normal and high SCH. Both devices showed comparable robustness in repeated measurements with a CV between 5.6% and 9.2%. Conclusion: We could show a significant correlation between both devices and a comparable differentiation between low and high SCH and comparable CVs. The real-life use demonstrated adequate acquiring and transmitting of in-vivo data to a smartphone and subsequently, transmitting to the secure-server with low numbers of missed transmissions (<0.2%) and missed measurements (<5%).引言与研究目的：基于电容的检测设备用于无创检测角质层含水量（stratum corneum hydration, SCH）已在皮肤病学与化妆品学研究中得到广泛应用。本研究旨在验证志愿者在真实生活场景下，使用基于蓝牙（无线）探头Corneometer®（CM825i）开展的角质层含水量无创自我检测的可靠性，该探头可通过智能手机应用将数据传输至中央服务器。探头与智能手机通过低功耗蓝牙（Bluetooth Low Energy, BLE）进行通信。智能手机端的数据通过HTTPS协议、采用TLS加密方式，安全传输至境外的远程服务器。本研究将CM825i的检测值与实验室环境下标准CM825的检测值进行相关性分析。主要研究终点为两款探头的相关性，次要研究终点为变异系数（coefficient of variation, CV）以及治疗前后的差值（delta值）。 材料与方法：本前瞻性观察研究共纳入18名健康志愿者（女性8名，男性10名）。志愿者在使用基础面霜DAC治疗的前后7天，分别在家中真实使用无线CM825i进行检测。 研究结果：两款检测设备均表现出显著且具有临床意义的相关性（p<0.0001；斯皮尔曼相关系数r=0.8647）。CM825i与CM825均可显著区分正常与高水平的角质层含水量。两款设备在重复检测中均表现出相当的稳定性，变异系数介于5.6%至9.2%之间。 研究结论：本研究证实两款设备间存在显著相关性，且在区分低、高水平角质层含水量方面表现相当，变异系数亦无显著差异。真实场景下的使用结果表明，该系统可有效完成活体数据的采集并传输至智能手机，后续再将数据传输至安全服务器，数据漏传率<0.2%，漏测率<5%。