Applicability of shear wave elastography for the evaluation of skin strain in systemic sclerosis

The assessment of skin fibrosis is vital for the diagnosis and monitoring of treatment in the systemic sclerosis (SSc)-a severe autoimmune disease. The elastography is a technique of skin fibrosis assessment through the evaluation of skin strain. We compared the efficacy of the shear wave elastography (SWE) and commonly used modified Rodnan skin score (RSS) in skin fibrosis assessment in SSc. The study included 40 SSc patients and 28 healthy individuals, with the exclusion of individuals with other skin/autoimmune diseases. Skin thickness using RSS and skin strain using SWE were assessed in the same 20 body localizations. Subjects' informed consent and the bioethics committee approval were obtained. Elastographic skin strain correlated positively with both partial and overall RSS values, with strong positive correlation (r ≥ 0.75) for hands and fingers localizations in particular. In SSc patients with normal RSS values, the elastographic strain was significantly higher than in healthy controls. Elastographic strain of fingers' skin evaluated in SWE is highly accurate for distinguishing SSc patients (sensitivity 0.897-0.923, specificity 0.929-0.964, positive predictive value 0.946-0.973, negative predictive value 0.867-0.900). ESW results are substantially more reproducible than those of RSS examination (intraclass correlation coefficients: 0.987 vs. 0.941). The shear wave elastography is more reproducible and has higher sensitivity than RSS in the evaluation of skin condition in SSc, especially in case of changes non-detectable on physical evaluation, indicating it might become a useful tool in SSc diagnosis.