Infrared-monitored cold response in the assessment of Raynaud's phenomenon

Background. Evaluation of treatments for Raynaud's phenomenon (RP) requires objective response parameters in addition to clinical activity scores. Thermographic monitoring of fingertip re-warming after cold challenge has been widely used but usually requires sophisticated equipment. We have previously shown that fingertip re-warming after cold challenge follows a first-order transient response curve that can be described by a single variable, designated s. Objectives. Here, we describe a novel device termed a duosensor, which records the s value upon cold challenge in an automated manner. Methods. We determined s values in healthy probands, patients with primary or secondary RP associated with autoimmune disease and patients with sclerodermaassociated RP following cold challenge, to determine assay variability, sensitivity and specificity. Results. Duosensor-based thermography exhibited low intraindividual variability in healthy probands. As expected, s values in RP patients were significantly increased compared with controls (8.08 ± 3.65 min vs. 3.23 ± 1.65 min). The duosensordetermined s value yielded a specificity of 94.6% and predictive value of 95.3% for the presence of RP in a retrospective analysis of 139 patients. Furthermore, in a cohort of scleroderma patients with RP, patient self-assessment of RP severity correlated with s values. Conclusions. Taken together, the present data suggest that s value determination provides a suitable outcome measure for clinical studies of novel RP treatments. As the duosensor is a simple stand-alone device requiring no supporting equipment and minimal personnel attention, it should allow RP activity monitoring even in clinical settings with minimal technical infrastructure.