What is the relationship between disease activity, severity and damage in a large Canadian systemic sclerosis cohort? Results from the Canadian Scleroderma Research Group (CSRG)

We studied the relationships between physician-assessed damage, severity and activity in a large, multicentre systemic sclerosis (SSc, scleroderma) cohort. We hypothesized that there is a relationship between disease activity and severity and damage, but that severity would be more strongly related to damage. A total of 520 SSc patients (87% women, mean age 56 years, mean 8.6 years disease duration, 39% diffuse SSc) were studied. The correlations between physician's global assessments of damage, activity and severity were determined overall and in a subset of early, diffuse SSc (n = 74). The mean (SD) patient global health score was 3.6 (2.4) on a 0-10 scale. Physician-rated severity, activity and damage were 2.8 (2.2), 2.3 (2.0), and 3.4 (2.4) respectively. Damage was more strongly related to severity (r = 0.744, P < 0.001) than activity (r = 0.596, P < 0.001). Damage was not related to disease duration (r = 0.046, P = 0.3). In early diffuse SSc, the correlations were: damage and severity 0.771 (P < 0.001), damage and activity 0.596 (P < 0.001), severity and activity 0.809 (P < 0.001). The relationships vary in the overall cohort versus the early diffuse SSc subset where activity, severity and damage appear more strongly related. Thus, the exact nature of the relationship between damage, activity and severity will depend upon the characteristics of the population studied.