SAT0640 SHEAR-WAVE ELASTOGRAPHY OF SKIN STIFFNESS IN SYSTEMIC SCLEROSIS: A FIVE-YEAR FOLLOW-UP STUDY

Abstract

Background: Measurement of skin involvement is essential for diagnosis and assessment of prognosis in systemic sclerosis (SSc). The mRSS is the gold standard measure of skin thickness. The mRSS has been criticised for being associated with high inter-observer variability and being too insensitive to detect relevant changes in skin thickness over time. Previously, our group demonstrated that shear-wave elastography (SWE) offers a potential for objective and quantitative assessment of skin involvement in SSc patients.1 However, no studies have evaluated its sensitivity to change over-time. Objectives: To assess changes in skin stiffness in SSc patients using SWE over-time. Methods: This study included 19 SSc patients [89.5% females; age 57.5 years (10.3), 53% with limited form; disease duration 11.4 years (8.5)] at baseline and, 13 healthy controls [69.2% females; age 53.4 years (11.5). Skin stiffness was measured by SWE, using virtual touch image quantification, at the 17 sites corresponding to the mRSS, in each participant, at baseline and follow-up [a mean of 4.9 ((4.6-4.9) years later]. mRSS was performed at both time points. Differences between groups were analysed using the related-samples Wilcoxon Signed Rank test. Results are presented as median (interquartile range (IQR)). Results: In SSc patients, skin stiffness measured by SWE decreased in a strongly significantly way (p≤0.001), over time at all skin Rodnan sites, except the fingers (table 1). Interestingly, the same was observed in controls for all sites, except the leg. The effects of normal ageing correspond to 30 to 60% of the changes observed in SSc. Local Rodnan scores only decreased significantly at the forearms and fingers of SSc patients. The reduction of mRSS at the fingers did not correspond to improvements in SWV. Shear wave velocity (SWV) measurements correlated with mRSS both at baseline (rs:0.56; p=0.0001) and at follow-up (rs:0.74; p=0.0001). Conclusion: Although preliminary, this study provides the first evidence suggesting that 1. SWV of the skin is more sensitive to change over time than mRSS; 2. Skin stiffness reduces significantly over time in normal controls, and 3. Normal skin ageing may contribute to the overall decrease of SWV with time in SSc. Our results highlight the discriminant ability of SWV in detecting subtle skin changes not identified by mRSS. SWV may offer a significant improvement in the evaluation of skin stiffness and may provide relevant insights into the biology of healthy and scleroderma skin. Studies including a larger number of patients in different phases of skin involvement and data on normal reference values of these ultrasound measurements are needed to reach a definitive validation.