A systematic review of ultrasonography as an outcome measure of skin involvement in systemic sclerosis

The modified Rodnan skin score is widely accepted as a validated tool to assess skin involvement in systemic sclerosis, which is a hallmark of this heterogeneous disease. Ultrasonography is increasingly being utilized in the study of other rheumatic diseases. The utility of ultrasonography to measure skin thickness in systemic sclerosis has been explored since three decades ago. The aim of this review was to examine the validity of ultrasonography as an outcome measure of skin involvement in systemic sclerosis. Original articles in English, published before December 2010, pertaining to the use of B mode ultrasound assessing skin involvement in systemic sclerosis were reviewed. Data were extracted with a focus on criterion and construct validity, reproducibility and responsiveness to change. Seventeen papers were analyzed. Skin thickness was most commonly studied, although skin echogenicity has also been examined. There was heterogeneity with regards to subjects, definitions used and sites imaged. Although there was limited information regarding reliability, when reported, the results showed excellent reproducibility. There was also a lack of construct and criterion validity and evidence for sensitivity to change. Ultrasound has potential as an outcome measure in systemic sclerosis. However, more work needs to be done in order to prove that it is a feasible outcome measure with proven validity.