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Abstract
Background Optical Coherence Tomography (OCT) of the skin has been proposed as imaging biomarker of fibrosis in Systemic Sclerosis (SSc) (1). However, over the past few years, growing efforts have been made to enable OCT to the study of human skin microcirculation including human nailfold (2). Dynamic OCT (D-OCT) is a newly developed OCT technology that allows detection of blood flow in vivo in addition to the images of traditional OCT scans (3).
Objectives Aims of this study were: 1) to evaluate face/criterion validity and feasibility of nailfold capillary D-OCT imaging as compared with nailfold video-capillaroscopy (NVC) capillary patterns in SSc patients; 2) to investigate whether D-OCT could offer a complementary value to NVC through the 3-dimensional reconstruction and quantification of nailfold capillary abnormalities in SSc patients.
Methods Fifty subjects including forty SSc patients all fulfilling 2013 EULAR/ACR classification criteria (10 with normal/non-specific, 10 with early, 10 with active, 10 with late capillary pattern respectively) and ten age/gender-matched healthy volunteers (HV) were enrolled in this study. All subjects had NVC done on 8 fingers and classified according to the capillary pattern. Nailfold of the finger with the worst capillary score in SSc patients and the 4th finger (the most affected in the SSc groups) of the dominant hand in subjects with normal capillary pattern was subsequently scanned using Vivosight D-OCT (Michelson Diagnostics Ltd., Kent, UK). D-OCT images were analyzed using the proprietary software tool to extract a quantitative measure of the speckle variance (SV)-signal. Results were expressed as mean±standard error. Statistical analysis was performed using GraphPad Prism software V.7.0.
Results The finger with the worst capillary score was the 4th (83%) in the SSc patients. The typical nailfold capillary features seen at NVC were visualized at D-OCT images. Representative images are shown in figure 1. Each nailfold D-OCT scan lasted 60 seconds, was well tolerated and did not require use of gel or immersion oil. OCT mean SV-signal measurements were significantly different between HV and SSc patients with any specific capillary pattern (0.16±0.02 vs 0.10±0.01, p=0.0028) and between SSc patients without and with specific capillary pattern (0.14±0.01 vs 0.10±0.01, p=0.02). The mean SV-signal was higher in HV than in SSc patients without specific capillary pattern however the difference was not statistically significant. When analyzing the three specific capillary patterns, SV-signal measurements were not significantly different. Interestingly, within the late capillary pattern, mean SV-signal was significantly lower in patients displaying capillary loss as main feature compared with those with remarkable neoangiogenesis (p=0.03).
Conclusions D-OCT is a feasible technique able to reproduce the capillary changes seen at NVC in SSc patients. More importantly D-OCT could offer a complementary value to quantify peripheral blood flow at capillary level. Future longitudinal studies are needed to evaluate the sensitivity to change over time and the potential of D-OCT as quantitative outcome measure of microvasculopathy in SSc.
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References
Disclosure of Interest None declared