Shear wave elastography-based skin assessment system for systemic sclerosis: a supplement or alternative to conventional ultrasound?

BACKGROUND: Although shear wave elastography (SWE) has been found to have the potential to evaluate skin lesions in systemic sclerosis (SSc), current research fails to answer the following questions: (I) can high-frequency ultrasound (HFUS) and SWE at multiple sites throughout the body distinguish SSc subtypes; (II) is HFUS and SWE at every site equally affected by clinical characteristics; and (III) is SWE a supplement or a choice to HFUS. This prospective study aimed to compare the value of SWE-based skin stiffness and HFUS-based skin thickness in distinguishing different SSc subtypes, verify the influence of clinical features on SWE and HFUS, and provide a basis for the screening of the optimal evaluation sites and indicators in the future. METHODS: Forty-nine limited and 51 diffuse SSc patients were included in this study. Their skin was assessed at 17 sites by palpation using the modified Rodnan skin score (mRSS), skin thickness measured by HFUS, and skin stiffness by SWE. Clinical features, including age, sex, body mass index, and disease duration, were collected. RESULTS: The diffuse SSc patients had higher skin stiffness at most sites (P<0.05), except for the finger, foot, and forehead, and a thicker skin layer at most sites (P<0.05), except for the finger. The area under the curve (AUC) of HFUS, SWE, and the combination of the two in distinguishing diffused and limited SSc were 0.866, 0.921, and 0.973, respectively. The differences were statistically significant (combination vs. SWE, P=0.002, combination vs. HFUS, P=0.021). Longer disease duration was associated with a thinner skin layer at the forearm, arm, chest wall, abdominal wall, and thigh in limited SSc, including the leg in diffused SSc. SWE was less affected by clinical features than HFUS. SWE could achieve greater discrimination between different mRSSs at multiple sites, such as fingers and arms, than HFUS. CONCLUSION: For the assessment of SSc skin, SWE has several advantages over HFUS, including less influence by clinical features and greater sensitivity to discriminate different mRSSs. SWE has the potential to become a primary imaging assessment tool as well as HFUS.