Is there a better way to differentiate Primary and Secondary Raynaud’s?

Date: Wed 17th October 2018

A study from Japan has devised a test which researchers claim could prove whether a patient has primary or secondary Raynaud's.

The study, 'A non-Invasive Technique for the Evaluation of Peripheral Circulatory Functions in Female Subjects with Raynaud's Phenomenon', devised a quick and non invasive approach to measuring circulation problems in women while claiming to distinguish between primary and secondary Raynaud's.

The study gathered Group A - ten women with primary Raynaud's and Group B - seven women who had Secondary Raynaud's (alongside a connective tissue condition). As the control group, 17 women were enrolled who had no signs or symptoms related to Raynaud's phenomenon.

Researchers used a common method to measure finger skin temperature (FST), combined with local cooling of the hand to stimulate vasoconstriction. They also used the less common method of the use of laser-Doppler flowmetry (LDBF), a noninvasive approach, to measure finger blood flow (FBF).

Overall, the FST (finger skin temperature) and FBF (finger blood flow) tests were reliable measures of Raynaud's phenomenon. The FST test was able to positively predict Raynaud's 85% of the time, while the FBF test was able to positively predict Raynaud's 82% of the time.

Initial FST measurements of those in the primary Raynaud's group were lower (average of 25.3 degrees Celsius, or 77.5 degrees Fahrenheit) compared with the Group B (28.3 degrees Celsius, or 82.9 degrees Fahrenheit), and the control group (30.7 degrees Celsius, or 87.2 degrees Fahrenheit).

Subjects in all three groups experienced a decrease of about 10 degrees Celsius in mean FST during the one-minute cold immersion test and no significant differences could be detected. The recovery patterns in groups A and B were similar during the five-minute recovery period, with finger temperatures gradually increasing. The recovery rate of FST was significantly lower in the primary Raynaud's group (71%) compared to the control group (85%).

Similarly, the mean value of FBF in the primary Raynaud's group was recorded at a much lower level compared to those with secondary Raynaud's phenomenon and the control group. After the one-minute cold immersion, FBF gradually recovered starting at two to three minutes. After five minutes, the recovery rate of FBF in the primary Raynaud's group was lower (32.8%) compared with the secondary Raynaud's group (56.6%) and the control group (81.6%).

According to the team, the method described represents a simple and quick setup with a series of measurements. With good sensitivity and specificity, this test was capable of distinguishing patients with either primary or secondary Raynaud's, and could monitor changes in peripheral circulatory function in patients.

Sourced from Stacy Grieve at