High-frequency ultrasound of the skin in systemic sclerosis: an exploratory study to examine correlation with disease activity and to define the minimally detectable difference

Abstract

BackgroundThickened skin is a major clinical feature in patients with systemic sclerosis (SSc). We investigated changes of skin thickness in patients with SSc using both high frequency ultrasound (HFU) and the modified Rodnan skin score (mRSS) to evaluate the feasibility of application of HFU in skin involvement and the relationship between HFU and clinical profiles.MethodsWe recruited 31 consecutive patients with SSc and 31 age-matched and sex-matched healthy controls in this prospective, cross-sectional study. Skin thickness was measured by an 18-MHz ultrasonic probe at five different skin sites. Total skin thickness (TST) and skin thickness using categorical mRSS scores were recorded and compared to HFU. The European Scleroderma Trial and Research (EUSTAR) group Disease Activity Index (EUSTAR-DAI) and other clinical manifestations were assessed and analyzed.ResultsTST in patients with SSc was thicker than in healthy controls (P < 0.001), and correlated positively with total mRSS and the EUSTAR-DAI and correlated negatively with disease duration (P < 0.05). Patients with higher TST had higher EUSTAR-DAI, mRSS, C-reactive protein (CRP) and lower diffusing capacity of the lung for carbon monoxide (DLCO) (P < 0.05). Even in patients who on clinical assessment were assigned an mRSS that suggested the skin thickness was normal. This was also true to mRSS locally of 1 and 2 (P < 0.01). The area under the receiver operator characteristic (ROC) curve was 0.831 and yielded sensitivity of 77.4% and specificity of 87.1% at the predicted probability of 7.4 mm as the optimal cutoff point to access skin thickness.ConclusionsIn the study, HFU was able to measure skin thickness, it correlated quantitatively with a valid measure of SSc activity, and a minimal detectable difference was identified.Electronic supplementary materialThe online version of this article (10.1186/s13075-018-1686-9) contains supplementary material, which is available to authorized users.

Ultrasound assessment of skin thickness and stiffness: the correlation with histology and clinical score in systemic sclerosis

“…In terms of sensitivity, prior reports have shown the advantage of ultrasound in detecting subclinical skin thickening which was not perceivable by physical examination [10,11]. In the current study, we further revealed that patients with exactly the same mRSS could have markedly different ultrasound-measured skin thickness and skin stiffness.…”

“…Skin ultrasound has been recognized as a valuable supplement to clinical skin assessment in SSc. First, subtle skin thickening was detectable by ultrasound even in the skin areas with a normal mRSS [10,11]. Second, ultrasound was more sensitive to treatment-induced skin changes than clinical skin scores [12].…”

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

“…With a progress in diagnostic imaging, researchers focused their interest on the applicability of ultrasonography for the evaluation of the severity and extent of skin fibrosis in SSc [13,14]. The ultrasound elastography is an ultrasonographic technique suitable for the quantification of skin fibrosis, indicating not the thickening of the skin, but its strain-a parameter, which can be considered as a more detailed marker of a change of the skin structure [15].…”

The Skin ultrasound in systemic sclerosis patients: an update

“…This was followed by the availability of ultrasound machines equipped with higher frequency probes (i.e. [18][19][20][21][22][23][24][25][26][27][28][29][30], which allowed for a more widespread use of ultrasound for the study of skin thickness. In fact, these machines provide a better visualization of superficial skin structures, including epidermis, dermis and subcutaneous fat tissue, thus making it possible to make quantitative (i.e.…”