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ItemDevelopment of the Scleroderma Clinical Trials Consortium Damage Index (SCTC-DI): a novel instrument to quantify organ damage in systemic sclerosisFerdowsi, Nava ( 2018)Objective: Systemic Sclerosis (SSc) is a multi-organ connective tissue disease resulting in fibrosis of the skin and internal organs. We sought to develop the first damage index (DI) in systemic sclerosis (SSc). Methods: Following systematic review of the literature focusing on methodology used to develop damage indices in other rheumatological conditions, the following methods were used to develop the SCTC-DI. The conceptual definition of organ damage in SSc was determined through consensus by a working group of the Scleroderma Clinical Trials Consortium (SCTC). Systematic review of the literature and consultation with three experienced patient partners and 7 non-rheumatologist experts produced a list of potential items for inclusion in the DI. The following steps were used to reduce the items; (1) Expert members of the SCTC (n=331) were invited by email to rate the appropriateness of each item for inclusion in the DI using a web-based survey. Items with >60% consensus were retained; (2) Using a prospectively acquired Australian cohort data set of 1,568 patients followed for a mean of 4.8 years, the univariable relationships between the remaining items and the end points of mortality and morbidity (physical component summary score of the Short Form 36) were analysed, and items with p value < 0.10 were retained; (3) using multivariable regression analysis against the above endpoints, coefficients were used to determine a weighted score for each item; (4) internal and external retrospective validation was performed to demonstrate construct and criterion validity. Results: Ninety-three (28.1%) complete survey responses were analysed; 58 of 83 items were retained. The univariable relationships with death and/or morbidity endpoints were statistically significant for 22 items. One further item was forced into the multivariable model by experts, due to clinical importance, to create a 23-item weighted SCTC Damage Index (SCTC-DI). Conclusions: Through the combined use of consensus and data driven methods, a 23-item SCTC-DI was developed. Future prospective validation is planned.