Digital-Artery-Closing Temperatures: An Objective Index of Severity in Raynaud's Phenomenon

Abstract

Evidence suggests that the color changes of Raynaud's phenomenon (RP) are initiated by spasm of the digital arteries. High-frequency A-mode ultrasound can be used to measure digital artery diameters, and in a group of patients suffering RP, the authors used it to monitor the development of digital artery spasm in fingers that had been progressively cooled. The present study evaluated the reproducibility and value of the temperature at which digital artery spasm occurs (digital-artery-closing temperature) as an objective index of RP severity. Forty-five subjects suffering RP were included (32 suffering primary RP and 13 secondary RP). All were assessed clinically by an independent physician and classified as suffering mild, moderate, or severe RR In 3 of these subjects, digital-artery-closing temperatures were determined on five separate days. The coefficients of variation for digital-artery-closing temperatures recorded in the 3 subjects were low (< 4%), confirming reproducibility. The technique failed in 1 subject suffering severe RP. In the 44 remaining subjects, digital-artery-closing temperatures correlated with clinical assessment. The mean digital-artery-closing temperatures and standard deviations for the three groups were: mild=18.31±1.07°C; moderate=20.83±1.32°C; severe = 25.53±1.38°C. The differences in closing temperatures between the groups were highly significant (P < 0.001, Mann Whitney). The maximum digital artery diameters recorded in the primary RP (including vibration white finger) subjects (Mean±Std Dev=1.21±0.14 mm) were larger than those in the secondary RP subjects (Mean±Std Dev=0.88±0.17 mm). This difference was highly significant (P < 0.001, Mann Whitney).