Freezing fingers syndrome, primary and secondary Raynaud's phenomenon: characteristic features with hand thermography.

The aim of the present study was to establish a thermographic model of healthy subjects' hands and compare it with a model of the hands of patients with freezing fingers syndrome, a group usually regarded as a healthy population. A further aim was to establish the thermographic parameters that distinguish primary Raynaud's phenomenon (RP) from secondary RP. The study was conducted on a group of 74 subjects, divided into 3 groups: patients with freezing hands symptoms (G1), those with primary RP (G2), and those with limited scleroderma (G3). In addition, 69 healthy volunteers served as a control group (G4). The most distinctive features of healthy subjects' hands are the thermal symmetry between left to right measurements (ΔT<0.5°C) and between mean temperatures of the metacarpus and digits (ΔT<0.5°C (1°C maximum)). A negative correlation was found between mean hands temperature and age of subjects in G4 (p<0.0001). All the temperatures observed in G4 subjects were significantly higher than among patients in G1, G2 and G3 (p<0.001). No significant differences were found between mean temperatures in G2 and G3. RP should be suspected when differences between mean temperatures of the metacarpus and digits are ≥to 3ºC. Moreover, we suggest that a cut-off point >1ºC is established for subjects with "freezing" symptoms.