An objective method to estimate the severity of Raynaud phenomenon: digital blood pressure response to cooling

The treatment efficacy of patients with Raynaud phenomenon (RP) is determined from the decrease in severity of this condition, usually based on a decrease in frequency of RP attacks as reported by patients in a diary. Although subjective, this method is still the main endpoint measure in clinical trials. The results of patients' digital blood pressure responses to cooling were compared with the reported RP attack frequency to determine whether the former could be used to estimate the severity of RP. The effect of local finger cooling on the digital systolic blood pressure was tested at 30 degrees C, 20 degrees C, 15 degrees C and 10 degrees C on 136 subjects with RP. The RP attack frequency was dichotomized into daily versus less than daily attacks. The frequency of attacks and the digital systolic pressure (DSP) showed a significant association at all cooling temperatures (those with daily attacks showed lower DSP than those with less frequent attacks). In addition, patients experiencing daily attacks of RP showed a zero reopening pressure at higher local temperatures than those with less frequent RP attacks. These results demonstrate that the response of the digital systolic blood pressure to cooling is closely associated with the RP attack frequency and therefore can be considered as an objective estimate of RP severity. This physiological measurement should be most useful in evaluating the clinical course of RP and the effect of its treatment, provided it is measured under standardized conditions.