• Systemic Sclerosis
• Outcomes research
• Patient perspective
• Disease Activity

Dobrota et al1 have analysed the EUSTAR (EULAR Scleroderma Trials and Research) systemic sclerosis (SSc, scleroderma) database using a subset of diffuse cutaneous SSc (dcSSc) to determine predictors of skin improvement over 1 year in randomised trials. The idea is to enrol more informative patients in a randomised controlled trial (RCT), as incident dcSSc is rare. However, you could want patients who progress/worsen (if not on effective treatment) or those who regress/improve more when on treatment, or some of each subgroup in the sample studied. More than 900 patients were included in the EUSTAR early dcSSc study,1 and like a Bell curve, with a smaller tail, a quarter improved, two-thirds had no change and one-tenth worsened. In order to have a sample size that is enriched for patients who may improve with effective treatment compared with a control, or conversely may worsen without effective treatment, then more informative patients are included and the study size can be smaller. They found that by varying the baseline modified Rodnan skin score (mRSS), the proportion of those who regressed went from 13% to 19% if the mRSS was <18 to 25, respectively. Therefore, the range of mRSS from 18 to 25 was most likely to enrich for those who would progress over an observation period. This can simply be that patients in mid-range skin scores in early dcSSc do not have as much of a floor or ceiling effect; that is, very low scores may worsen but are unlikely to improve and very high mRSS scores are unlikely to progress as they already have a high amount of skin involvement (ceiling). Conversely, they observed that 44% improved if the mRSS was more than 25. The mean mRSS was 16 at baseline in the EUSTAR analysis,1 so not all patients would …