Using a smartphone app to monitor Raynaud's attacks and quantify skin colour changes-towards objective outcome measures for Raynaud's.

Objectives: Our overall aim was to develop a smartphone app to collect photographic images of Raynaud's phenomenon (RP) attacks alongside patient reported outcome measures (PROMs). Specific objectives included assessing the feasibility of patients documenting RP attacks using mobile phones, developing image analysis methods to document colour change, and comparing photographic parameters to 'non-imaging' app and paper diary parameters.

Methods: Study 1: 36 patients with systemic sclerosis (SSc)-related RP photographed RP attacks over 15 days as well as completing an RP paper diary. Study 2: 40 patients with either SSc-related or primary RP used a smartphone app to collect, over 15 days, photographic images and data including frequency and severity of attacks. In both studies, mean colour change during each attack (indicating severity) was quantified by the Bhattacharyya distance.

Results: Study 1: 24/36(67%) patients completed the study of whom 22 photographed at least one RP attack (median number of attacks 12.5, range 1-53). 18/24(75%) patients preferred phone to paper diary documentation. 'Photographic' and 'paper diary' frequency (but not severity) of attacks correlated strongly: correlation co-efficient 0.71, 95% confidence intervals 0.41-0.87; p= 0.002. Study 2: 36/40(90%) completed the study, providing 1747 usable images from 456 RP attacks. ANOVA analysis demonstrated that RP colour change was significantly different with different values of RP attack severity (p< 0.001).

Conclusion: Collecting photographs of RP attacks and PROMS via a smartphone app was feasible and preferred by patients to data collection via paper diary, providing proof-of-concept for validation studies of app-based outcome measures for RP.