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Introduction Current treatments for Raynaud’s phenomenon (RP) tend to be poorly effective; clinical trials are challenging. Thermographic response to a cold challenge has been validated as an outcome measure with the exception of sensitivity to change. SATISS, an international collaborative observational study aimed to complete validation.Material and Methods Patients with systemic sclerosis spectrum disorder-related RP, beginning a phosphodiesterase inhibitor attended on three occasions: Visits 1 and 2 (days 1, 14) pre-treatment, Visit 3 (day 29) after 14 days’ treatment (sildenafil, 20-25 mg, 2-3 times daily). At each visit, baseline hand temperature, cold challenge and 15-minute recovery were imaged simultaneously with standard and mobile thermography in a temperature-controlled laboratory (on Visit 3 this was 1-2 hours after the morning dose). Additionally, patients carried out daily mobile phone thermography self-imaging of their hands at home (morning and afternoon, figure 1).For baseline and home-based images, distal finger temperature was calculated. Post-cold challenge, the maximum temperature (MAX), area under the recovery curve (AUC) and gradient in the first 2 mins (GRAD) were calculated; all averaged over 8 fingers. Linear mixed-effects models were used to assess treatment effects.Results 38 participants were recruited from five centres. Eight participants withdrew, two had incomplete laboratory and three incomplete home-based imaging data. 28 participants were included in the analysis; 2M:26F, median age 57 (IQR 50–68) years, median disease duration 10 (IQR 3-15) years.Laboratory imaging: GRAD increased post-treatment as measured by both standard and mobile phone thermography (Visit 3 from Visit 1) e.g. estimates = 0.14°C/min; p = 0.270 (standard camera) and 0.29°C/min; p = 0.034 (mobile camera). MAX and AUC showed a non-significant trend for increase from Visits 1 and 2 to Visit 3 (figure 2).Home-based imaging: Thermography (afternoon only) showed significant finger temperature increase of 1.30°C post-treatment (p=0.021).Conclusions The trend for MAX, AUC and GRAD to increase on-treatment, using both standard and mobile-thermography, suggests that thermographic response to cold challenge is likely to be sensitive to change in the context of studies of vasodilatory treatments.The significant increase post-treatment in afternoon home-based temperatures (not seen with morning home temperatures or with laboratory-based (morning) temperatures) may be due to the time of sildenafil dosing and/or a greater number of home-based (daily) measures for analysis. These results suggest that ambulatory thermography should be further explored as an outcome measure in clinical trials.Abstract P.190 Figure 1Examples of thermal hand images taken by patients at homeAbstract P.190 Figure 2Box plots of laboratory imaging over visits 1-3 (V1, 2 and 3) standard camera (a-c) and mobile camera imaging (d-f) showing maximum temperature reached after cold challenge (MAX), area under the rewarming curve (AUC) and gradient of rewarming (GRAD)