Background Reduction in capillaries number is the defining feature of microvascular disease in Systemic Sclerosis (SSc) and it concurs to the ischemic manifestations of the disease. Digital Ulcers (DUs) are the major complication of ischemic peripheral vasculopathy.
Dynamic optical coherence tomography (D-OCT) is a recently developed imaging technique that allows non-invasive in vivo study of the microvasculature of the skin. In addition to the skin architecture and vessels morphology, it offers information about flow status, allowing the functional and quantitative evaluation of the microcirculation.1
Objectives To determine the face and content validity of D-OCT as outcome measure of the skin microvascular disease, assuming the presence of current DUs, distal to the DIP joints, as gold standard for ischemic peripheral vasculopathy in SSc.
Methods A total of 54 patients were enrolled in this cross-sectional study, including 18 SSc patients with current DUs (DU group); 18 SSc patients without current DUs (no DU group) and 18 patients with Raynaud's phenomenon and SSc specific ANA, who did not fulfilled ACR/EULAR 2013 classification criteria (SRP group).
For each patient, we performed a D-OCT scan on both index and middle fingers, on the dorsal aspect of the second phalanx, employing Vivosight Scanner (Michelson Diagnostics). The speckle variance signal of D-OCT images within the first mm of skin depth was extracted, quantified as area under the curve (AUC) and defined as Micro Vascular Flow (MVF).
MVF comparison between the groups was done using parametric or non-parametric tests as appropriate. Statistical Analysis was performed with SPSS V.22.
Results All three groups were comparable in terms of age and gender distribution (p>0.80 for both) as well as disease duration and clinical subset between the two SSc groups (p=0.839 and p=0.646, resp.). With a scan time <1 minute, D-OCT allowed the visualization and quantification of capillaries within the first millimeter of skin depth (Figure 1).
The distribution of MVF was not significantly different among the four fingers within each group (DU group: p=0.459, no DU group: p=0.953 and SRP group: p=0.616). On the contrary, the distribution and median MVF for all fingers was significantly different among the 3 groups: DU group=0.134 (IQR 0.121–0.134), no DU group=0.153 (IQR 0.132–0.153) and SRP group=0.167 (IQR 0.148–0.167) (p<0.0001), as well as in the DU group vs. no DU group (p<0.001) or DU vs SRP group (p<0.001).
Further, sub analysis of the DU group showed that 10 of the total 20 DUs were on the left index finger. Within this subgroup the MVF of patients on Sildenafil (n=6) was significantly higher than the rest of the group (0.148±0.021 vs. 0.113±0.019, p=0.03).
Conclusions MVF assessed by D-OCT is a quantitative, non-invasive surrogate outcome measure of severe peripheral ischemic vasculopathy in SSc. Longitudinal studies assessing its sensitivity to change will inform whether MVF can be used as end point of skin microvascular involvement in SSc.
C. Tolosa-Vilella et al. Semin Arthritis Rheum 46(2016):200–208.
Disclosure of Interest None declared
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