Assessing post-cold challenge recovery of thermography as a potential outcome measure in trials of SSc-related Raynaud's phenomenon.

Improved new medications for systemic sclerosis-related Raynaud's phenomenon (SSc-RP) are badly needed and better objective outcomes are required to enable this. Thermography imaging of hand cold-challenge offers potential as an outcome measure. To ensure standardisation between pre- and post-dose cold challenge assessments, it is important to understand the length of time required for patients to recover back to baseline finger temperatures after initial cold challenge. The aim of this study was to determine whether patients with SSc-RP would recover baseline finger temperatures within a 2-h period. Patients with SSc-RP underwent cold-challenge alongside thermography-imaged baseline and post-cold challenge recovery for 2 h. Twenty patients were recruited, eight (40%) had all eight fingers recover to baseline within 2 h, 13 (65%) had more than one finger recover. The median (IQR) time to maximum temperature was 48.43 (33.58-69.38) minutes. This study indicates that most patients will have one or more fingers recover within an hour. Even in those with established SSc it is reasonable to repeat cold challenge with a minimum one-hour interval in clinical trials, enabling pre- and post-dose cold challenges on the same day.