Objectives: To evaluate ultrasound Virtual Touch Imaging and Quantification (VTIQ) as a method for determining absolute skin stiffness in patients with systemic sclerosis (SSc).
Methods: Skin thickness, assessed by the modified Rodnan Skin Score (mRSS) and absolute skin stiffness, using VTIQ, were measured at all mRSS anatomical sites to quantify the shear wave velocity (in m/s) in 26 SSc patients and in 17 age- and gender-matched controls. Correlations between mRSS and absolute skin stiffness, and comparisons between patients and controls were analysed statistically using Mann-Whitney U tests and correlations between variables using Pearson's. P values <0.05 were considered significant.
Results: Shear wave velocity as a measure of skin stiffness was significantly higher in SSc than in controls in 11 out of 16 mRSS sites investigated. Shear-wave velocity was strongly correlated with the local mRSS in the following anatomical sites: forearm, hand, phalanx, and thigh. In the patient group, clinically unaffected skin could also be differentiated from healthy skin using shear-wave velocity.
Conclusions: VTIQ represents an innovative and promising technique that provides, for the first time, a non-invasive, absolute quantification of skin stiffness. Further studies of VTIQ are required, but this early study supports the clinical and scientific potential of this new measure of skin involvement in SSc.