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Systemic sclerosis (systemic scleroderma) is characterized by a heterogeneous range of clinical manifestations. Systemic sclerosis is classified into limited cutaneous systemic sclerosis and diffuse cutaneous systemic sclerosis subgroups based on the extent of skin involvement. Randomized controlled trials in scleroderma have mainly focused on diffuse cutaneous systemic sclerosis partly because the measurement of skin involvement, critical for evaluating a therapeutic intervention, is more dynamic in this subset. Nonetheless, limited cutaneous systemic sclerosis, the most common cutaneous subset (about two-third), is also associated with significant morbidity and detrimental impact on health-related quality of life. The lack of interventional studies in limited cutaneous systemic sclerosis is partly due to a lack of relevant outcome measures to evaluate this subgroup. Combining several clinically meaningful outcomes selected specifically for limited cutaneous systemic sclerosis may improve representativeness in clinical trials and responsiveness of outcomes measured in randomized controlled trials. A composite index dedicated to limited cutaneous systemic sclerosis combining such relevant outcomes could advance clinical trial development for limited cutaneous systemic sclerosis by providing the opportunity to test and select among candidate drugs that could act as disease-modifying treatments for this neglected subgroup of systemic sclerosis. This proposed index would include items selected by expert physicians and patients with limited cutaneous systemic sclerosis across domains grounded in the lived experience of limited cutaneous systemic sclerosis. This article reviews the reasons behind the relative neglect of limited cutaneous systemic sclerosis, discusses the current state of outcome measures for limited cutaneous systemic sclerosis, identifies challenges, and proposes a roadmap for a combined limited cutaneous systemic sclerosis-specific treatment response index.

Patient-reported outcome instruments provide valuable insight into disease-related morbidity known only to the patient and complement more objective outcome tools in the clinical trial setting. They are of particular importance in systemic sclerosis owing to the challenges around defining disease activity, the episodic nature of many disease-specific manifestations and the paucity of validated objective surrogate outcome measures for use in clinical trials. Early clinical trials of systemic sclerosis often incorporated legacy patient-reported outcome instruments, but the last 20 years has witnessed the emergence of several scleroderma-specific instruments that are now being routinely used alongside other outcomes in systemic sclerosis clinical trials. More recently, the value of patient-reported outcomes has been highlighted by their prominence in the American College of Rheumatology Combined Response Index for Systemic Sclerosis that has been utilized as the primary endpoint of recent clinical trials of early diffuse systemic sclerosis. This review considers the role and performance of the various patient-reported outcome instruments utilized in systemic sclerosis clinical trials, the current positioning of patient-reported outcome instruments within clinical trial endpoint models across the range of systemic sclerosis disease manifestations and, where applicable, we shall highlight areas for future research.

Introduction: The reliability of clinician grading of systemic sclerosis–related digital ulcers has been reported to be poor to moderate at best, which has important implications for clinical trial design. The aim of this study was to examine the reliability of new proposed UK Scleroderma Study Group digital ulcer definitions among UK clinicians with an interest in systemic sclerosis. Methods: Raters graded (through a custom-built interface) 90 images (80 unique and 10 repeat) of a range of digital lesions collected from patients with systemic sclerosis. Lesions were graded on an ordinal scale of severity: ‘no ulcer’, ‘healed ulcer’ or ‘digital ulcer’. Results: A total of 23 clinicians – 18 rheumatologists, 3 dermatologists, 1 hand surgeon and 1 specialist rheumatology nurse – completed the study. A total of 2070 (1840 unique + 230 repeat) image gradings were obtained. For intra-rater reliability, across all images, the overall weighted kappa coefficient was high (0.71) and was moderate (0.55) when averaged across individual raters. Overall inter-rater reliability was poor (0.15). Conclusion: Although our proposed digital ulcer definitions had high intra-rater reliability, the overall inter-rater reliability was poor. Our study highlights the challenges of digital ulcer assessment by clinicians with an interest in systemic sclerosis and provides a number of useful insights for future clinical trial design. Further research is warranted to improve the reliability of digital ulcer definition/rating as an outcome measure in clinical trials, including examining the role for objective measurement techniques, and the development of digital ulcer patient–reported outcome measures.