Sensitivity to change of the modified Rodnan skin score in diffuse systemic sclerosis-assessment of individual body sites in two large randomized controlled trials

Abstract

Objective. The modified Rodnan skin score (MRSS) is a standard outcome measure for skin disease in SSc and calculated by summation of skin thickness in 17 different body sites (total score=51). Our objective was to evaluate the sensitivity of change over time of individual body sites used in the calculation of total MRSS. Methods. We analysed two randomized placebo controlled clinical trials investigating the effect of either recombinant human relaxin or type I oral collagen in dcSSc. Both trials used MRSS as the primary outcome measure. We used a change of >10mm (on a 0-100 VAS) in the patient global assessment (PGA) as the clinically important improvement. We calculated the mean change and the effect size (ES) for each individual body site used in the total MRSS for each study. Magnitude of ES was assessed using Cohen's rule of thumb for ES. Results. In the relaxin and collagen studies, 71 of 199 patients (36%) and 54 of 129 (42%) of patients had an improvement >10mm on the PGA at 6 and 12 months, respectively. Total MRSS had large ES in both studies (0.85-0.98); the chest, forearms and hands had moderate ES (0.50-0.74); and the lower extremities, face, abdomen and fingers had small ES (0.16-0.49). Conclusion. Certain body sites (hands, forearms and chest) are more sensitive to change compared with other body sites in two randomized clinical trials. It remains to be seen whether decreasing the number of body sites by exclusion of relatively static areas would further increase the sensitivity to change over time of the total MRSS. © The Author 2009. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved.