AB0582 DIAGNOSING SYSTEMIC SCLEROSIS WITH PHOTOACOUSTIC AND HIGH-FREQUENCY ULTRASOUND IMAGING

Abstract

Background:Vasculopathy is already evident in early systemic sclerosis (SSc); Raynaud’s phenomenon and typical nailfoldcapillaroscopic findings are part of the criteria of very early diagnosis of SSc (VEDOSs) (1). As not all early SSc patients have alterations in their nailfoldcapillaries, there is need for other diagnostic tools. Photoacoustics(PA) and high-frequency ultrasound (HFUS) might be able to fulfill this need (2). The former can measure the oxygen saturation of hemoglobin by using short pulsed laser light while the latter can provide high-resolution images that allow measuring skin thickening distal from DIP joint, which could be used to determine skin involvement early.Objectives:We hypothesize that photoacoustics and high-frequency ultrasound can distinguish (early) SSc patients from individuals with primary Raynaud’s phenomenon (PR) by measuring the oxygenation (by PA) of the fingertip and skin thickening (by HFUS).Methods:In our cross-sectional study, we compared measurements of the third finger in (early)SSc patients with individuals with PR and healthy volunteers. Smoking and beta-blockage were exclusion criteria. The level of oxygenation (by PA) and skin thickness (by HFUS) were compared between groups. Nailfoldcapillaroscopy was performed on all subjects and analyzed for the pattern.Results:Thirty-one adult subjects participated in this study: twelve patients with SSc, 5 patients with early SSc, 5 volunteers with PR and 9 healthy controls.We found a significant difference in median (IQR) oxygen saturation between earlySSc patients 75.9% (IQR 75.1%-86.6%) and subjects with PR 94.1% (IQR 93.1%-94.5%) (p=0.0002) using the Wilcoxon rank-sum test (figure 1).Figure 1.Boxplot of saturation (%) per group.Measurements of skin thickening also showed a significant difference in early SSc patients compared to subjects with PR, respectively 0.5mm (IQR 0.4mm-0.5mm) vs. 0.3mm (IQR 0.3mm-0.3mm), P=0.0002 (figure 2).Figure 2.Boxplot of skin thickness (mm) per group.Conclusion:Our results demonstrate that photoacoustic and high-frequency ultrasound can distinguish between (early)SSc and PR in both oxygenation saturation and skin thickening. In a larger prognostic study we want to determine the value of photoacoustic and high frequency ultrasound in diagnosing earlySSc.