Hyperspectral imaging in systemic sclerosis-associated Raynaud phenomenon

BACKGROUND/PURPOSE: Lack of robust, feasible, and quantitative outcomes impedes Raynaud phenomenon (RP) clinical trials in systemic sclerosis (SSc) patients. Hyperspectral imaging (HSI) non-invasively measures oxygenated and deoxygenated hemoglobin (oxyHb and deoxyHb) concentrations and oxygen saturation (O(2) sat) in the skin and depicts data as oxygenation heatmaps. This study explored the potential role of HSI in quantifying SSc-RP disease severity and activity. METHODS: Patients with SSc-RP (n = 13) and healthy control participants (HC; n = 12) were prospectively recruited in the clinic setting. Using a hand-held camera, bilateral hand HSI (HyperMed™, Waltham, MA) was performed in a temperature-controlled room (22 °C). OxyHb, deoxyHb, and O(2) sat values were calculated for 78-mm(2) regions of interest for the ventral fingertips and palm (for normalization). Subjects underwent a cold provocation challenge (gloved hand submersion in 15 °C water bath for 1 min), and repeated HSI was performed at 0, 10, and 20 min. Patients completed two patient-reported outcome (PRO) instruments: the Raynaud Condition Score (RCS) and the Cochin Hand Function Scale (CHFS) for symptom burden assessment. Statistical analyses were performed using the Mann-Whitney U test and a mixed effects model (Stata, College Station, TX). RESULTS: Ninety-two percent of participants were women in their 40s. For SSc-RP patients, 69% had limited cutaneous SSc, the mean ± SD SSc duration was 11 ± 5 years, and 38% had prior digital ulcers—none currently. Baseline deoxyHb was higher, and O(2) sat was lower, in SSc patients versus HC (p < 0.05). SSc patients had a greater decline in oxyHb and O(2) sat from baseline to time 0 (after cold challenge) with distinct rewarming oxyHb, O(2) sat, and deoxyHb trajectories versus HCs (p < 0.01). There were no significant correlations between oxyHb, deoxyHb, and O(2) sat level changes following cold challenge and RCS or CHFS scores. CONCLUSION: Hyperspectral imaging is a feasible approach for SSc-RP quantification in the clinic setting. The RCS and CHFS values did not correlate with HSI parameters. Our data suggest that HSI technology for the assessment of SSc-RP at baseline and in response to cold provocation is a potential quantitative measure for SSc-RP severity and activity, though longitudinal studies that assess sensitivity to change are needed.