Both tissue temperature and recent physical activity may hinder blood flow, which could affect ultrasound measurement. “Our results strongly indicate that only cooling of the skin affects the amounts of ultrasound Doppler activity in the synovium of RA patients,” conclude the researchers who were led by Karen Ellegaard, PhD, of Frederiksberg Hospital in Frederiksberg, Denmark. “In contrast, heating and hand exercise did not affect the color fraction in any systematic way.”
“The results indicate that the accuracy of ultrasound Doppler measurements in RA is good which underlines its usefulness in diagnosis, disease progression assessment and monitoring of treatment.”—Karen Ellegaard, PhD
To arrive at their findings, the researchers utilized ultrasound Doppler in the wrists of 29 RA patients before and immediately after isometric exercise of the muscles of the hand and forearm, heating, and cooling of the hand. They assessed the amount of Doppler in the wrist joint by measuring the percentage of color in the synovium (the color fraction).
The color fraction decreased significantly after cooling of the hand, but the other interventions did not significantly affect the color fraction, the study showed.
Translating research into practice: cooling of the hand and Doppler exam don’t mix
“Cooling of the hand should, if possible, be avoided before an ultrasound Doppler examination of the wrist in patients with RA, because the amount of Doppler activity might be affected by low skin temperatures,” the study authors suggest.
“Studies on other physiological or pharmaceutical stimuli with possible effect on regional perfusion are required to fully clarify the accuracy of ultrasound Doppler measurements,” they conclude.
Reference
1. Ellegaard K, Torp-Pedersen S, Henriksen M, et al. Influence of recent exercise and skin temperature on ultrasound Doppler measurements in patients with rheumatoid arthritis - an intervention study. Rheumatology. [epub ahead of print Sept. 18, 2009].
