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Objectives: Distinction of dermal thickening at fingers is paramount in recognition of systemic sclerosis (SSc). Evaluation of skin thickening by modified Rodnan skin score (mRSS) might be challenging. Simple and practical tools are needed to help distinguishing (non-) thickened skin in daily practice. High frequency ultrasonography (HFUS) can reliably measure dermal thickness (DT). In this pilot study we search for a DT cut-off value (as a simple HFUS discriminator) to distinguish between healthy control (HC) and SSc skin at the left index finger (F2L)., Methods: DT evaluated by HFUS (18MHz probe) in SSc patients (2013 ACR/EULAR criteria) was compared with HC in a cross-sectional study. A cut-off value was selected by receiver operating characteristic (ROC) curve analysis., Results: 63 consecutive SSc patients (mean age 52±14 SD, 78% female) and 48 HC (mean age 36±14 SD, 62% female) underwent HFUS. Mean DT at F2L was 1.44 mm (± 0.39 SD) in SSc patients and 1.06 mm (± 0.19 SD) in HC. Based on ROC-curve analysis, a DT cut-off of 1.5 mm is proposed as simple HFUS discriminator between HC and SSc, at a specificity of 1 and a sensitivity of 0.32. The final model had an area under the curve of 0.83 (95%CI 0.75-0.90)., Conclusions: A simple HFUS discriminator between skin thickness of HC versus SSc, i.e., DT as measured at F2L, at a cut-off of 1.5 mm, is proposed for daily use in rheumatology clinics. Further validation should be executed through prospective multicentric cohorts.

Objectives: Body mapping of normal values of skin thickness and hardness may be a useful aid in daily practice. By employing non-invasive techniques, our pilot study provides these values in healthy individuals using high frequency ultrasound (HFUS) and durometry in areas used to evaluate the modified Rodnan skin score (mRSS)., Methods: One-hundred-fifty-two healthy volunteers from Ghent and Genova University Hospitals (mean ages 31.2, 35.5, and 64.9 years), were evaluated to exclude rheumatologic diseases. HFUS and durometry were used to assess the dermal status in mRSS areas. Exploratory analyses were performed to assess the impact of demographic and anthropometric characteristics on intra-subject skin measurements. Statistical analysis was performed with Datatab®., Results: The upper and lower arms exhibited significantly higher durometry values and lower dermal thickness compared to the trunk regions, underscoring distinct variations across these areas (all p<0.05). The hardest skin was found on the finger, while the thickest dermal measurements were at the abdomen and thighs. Dermal thickness was higher in men in multiple areas in the three cohorts, albeit with relatively modest effect sizes (r coefficients ranging between 0.02 and 0.6). Despite the presence of significant inter-group differences in dermal thickness, HFUS mapping showed similar topographical distributions in both centres., Conclusions: Our study offers a comprehensive skin mapping status in healthy individuals. Key findings indicate lower dermal thickness in the upper arms, legs, and feet, and higher skin hardness in peripheral areas like fingers, compared to truncal regions.This skin mapping pilot study might provide the normal distribution values in outpatient clinics for physicians to be used when comparing the same areas in pathological conditions like systemic sclerosis-related fibrotic skin.