High frequency ultrasound measurement of digital dermal thickness in systemic sclerosis

Background: Currently, assessment of dermal thickness in systemic sclerosis (SSc) is performed by palpation and assessment using the modified Rodnan skin score (mRSS). Objective: To verify whether high frequency ultrasound (US) may be a reliable and a reproducible method to measure digital dermal thickness. Methods: In 70 patients with SSc, skin thickness was evaluated with US by 2 observers at 2 different sites on the second digit of the dominant limb to determine the interobserver variability. Patients and controls were examined twice by the first observer for intraobserver variability. Patients were divided into three subgroups according to the phase of the disease (oedematous, fibrotic or atrophic). Results: At both examined areas, US showed a significant dermal thickening (p<0.001) in the whole group of patients with SSc. A low intraobserver and interobserver variability was found. A highly significant correlation between the global mRSS and the local dermal thickness at the two examined sites (p=0.032, p=0.021) was detected. Skin thickness was significantly higher in the oedematous than in the fibrotic group (p<0.001) and significantly higher in the fibrotic and the oedematous group (p<0.001) than in the atrophic group (p<0.002). Conclusions: US is a reliable tool giving reproducible results, and is able to detect digital dermal thickening in SSc