Data of 5 early SSc patients, 12 SSc patients, 5 individuals with primary Raynaud's phenomenon (PRP) and 9 healthy volunteers (HV) was analyzed. Table 1 summarizes the baseline characteristics.
Table 1. Baseline characteristics.
|
Early SSc
( n=5 )
|
SSc
(n=12)
|
PR
(n=5)
|
HV
(n=9)
|
Age in years (median, IQR)
|
40 (32-58)
|
59 (46-62)
|
29 (25-44)
|
34 (26-52)
|
Female (%)
|
80%
|
42%
|
60%
|
33%
|
Disease duration in months (median, IQR)
|
12 (5-29)
|
88 (33-108)
|
-
|
-
|
mRSS (median, IQR)
|
-
|
5 (3-10)
|
-
|
-
|
ILD (%)
|
-
|
58 %
|
-
|
-
|
Comediaction use (%);
- Calcium antagonist
- Angiotensine 2 inhibitor
- Endotheline antagonist
- None
|
40%
0%
0%
60%
|
42%
17%
8%
33%
|
-
-
-
100%
|
-
-
-
100%
|
Early SSc: early Systemic Sclerosis. SSc: Systemic Sclerosis. PR: primary Raynauds phenomenon. HV: Healthy volunteer.
Disease duration from first non Raynaud phenomenon.
mRSS: modified Rodnan Skin Score.
ILD: Interstitial lung disease.
Figure 1 shows the PA and HFUS images of a healthy volunteer and a SSc patient. The red line in the images delineates the region of interest for measuring oxygen saturation. The dark red color in the picture represents full oxygenation (100%). As shown in figure 1 there is a big difference in oxygenation between the healthy volunteer (a) where the area of interest is completely red and the SSc patient (b) where this area is fragmented light red. These findings indicate normal oxygenation in the healthy volunteer and a decreased oxygenation in the SSc patient. To calculate the degree of oxygenation in the area of interest, an average estimation of oxygen saturation over the region in 2 minutes is extracted. The dark regions are not taken into account when estimating the average oxygen saturation.
On the left the ultrasound image where the red line delineates the region of interest where the oxygen saturation was estimated and the white areas indicate a region with no oxygenation.
On the right side the nailfoldcapillairy microscopic images of a healthy volunteer with normal density and normal capillaries and below an image of an active SSc patern on nailfoldmicroscopy with a decreased density, giant capillaries and hemorrhages.
Oxygenation saturation
There is a significant difference in oxygen saturation between the early SSc patients with or without the SSc patients and PRP individuals (p = 0.0002). The median oxygen saturation was 75.9% (IQR 75.1%-86.6%) for early SSc, 81.0% (IQR 68.1%-85.1%) for SSc and 94.1% (IQR 93.1%-94.5%) for PRP individuals, respectively (figure 2a).
Comparing early SSc patients with PRP individuals, also a statisticaly significant difference in oxygen saturation (p =0.0079) was observed. Figure 2 illustrates that oxyensaturation of PRP individuals is comparable with healty volunteers.
Skin thickening
Figure 3 shows a HFUS measurement of the skin of a healthy volunteer and an SSc patient and there is a clear difference in skin thickening and structure. The median skin thicknes for the early SSc group was 0.50mm (IQR 0.45mm-0.52mm), 0.53mm (IQR 0.42mm-0.59mm) for the SSc group and 0.28mm (IQR 0.26mm-0.27mm) for the PRP group. We found a significant difference in skin thickness between the combined group of all SSc patients and PRP individuals and between early SSc patients versus PRP individuals. (p=0.0079).
In addition, we explored the association between capillary density and oxygen saturation. Figure 4 shows the scatterplots of the four groups. The spearman rank correlation coefficient was 0.68.
High frequency ultrasound image of the finger with a notation indicating different parts of the finger. The upper image is for healthy volunteer and lower image is SSc patient.
Oxygenations saturation (%). Density (capillaries per mm). Spearmans rank correlation coefficient 0.68. SSc Systemic Sclerosis. Early SSc early Systemic Sclerosis. PRP primary Raynaud phenomenon. HV Healthy volunteer.