Background/Purpose: Effective treatments for systemic sclerosis (SSc) related Raynaud’s phenomenon (RP) are badly needed but clinical trials have been hampered by the lack of objective outcome measures. Laser speckle contrast imaging (LSCI) and thermography are two non-invasive measures of blood flow that show excellent potential but require further investigation to prove their suitability as outcome measures in multi-centre clinical trials. The main aim of this multi-centre study was to determine the validity and reliability of LSCI and thermography. This abstract reports the first step in a more comprehensive analysis; the repeatability of the techniques as assessed by a local assessor at each site.

Methods: 158 patients with RP secondary to SSc were recruited from 6 specialist SSc centres in the UK. Patients attended their local centre on 2 consecutive days. They underwent a cold challenge; 15^oC water submersion of gloved hands for 1 minute, then un-gloved reperfusion and rewarming at 23^oC room temperature. Baseline and changes in blood flow and temperature over 15 minutes post challenge were imaged simultaneously using LSCI (relative perfusion) and thermography (skin temperature, an indirect measure of perfusion), respectively. Parameters for both perfusion and temperature were calculated locally and data analysis was performed centrally. The distal dorsal differences (DDD) of each hand were calculated from baseline images. The area under curve (AUC), maximum value (MAX), and gradient (GRAD) in first two minutes were calculated from the post challenge data of the fingers. Data were averaged across 8 digits for each patient to obtain a single measurement for each parameter for each technique at both visits. Test-retest reliability was assessed using intra-class correlation coefficients (ICC) using linear mixed models (R version 3.2.3) where an ICC of 0.60 is regarded as substantial reliability (Landis and Koch 1977).

Results: Median age was 63.3 years (IQR 53.8–69.8), 84% were female, median SSc symptom duration was 9.6 years (IQR 4.5 – 17.4), and 77% had limited cutaneous SSc. Both techniques had substantial reliability for AUC.  Thermography reliability across all parameters varied from moderate to strong (GRAD 0.56 to MAX 0.72) and LSCI varied from moderate to substantial (GRAD 0.46 to AUC 0.67) (table 1). Reliability of the two techniques has higher overall ICCs for thermography, suggesting marginally greater reliability of thermography in this sample.

Conclusion: This is the first multi-centre study examining reliability of LSCI and thermography in patients with RP secondary to SSc, and these are the preliminary findings from local analysis. The results and analysis are encouraging, overall, LSCI and thermography demonstrated moderate to strong reliability (and therefore good potential as outcome measures of digital vasculopathy), although thermography appears to be marginally superior to LSCI. Table 1. ICCs (Logged for non-normality where necessary) for summary measures of response to cold challenge under LSCI and thermography.