The Sjogren's Syndrome Damage Index--a damage index for use in clinical trials and observational studies in primary Sjogren's syndrome

Abstract

Objective. To validate a tool for assessment of accumulated damage in patients with Primary SS (PSS). Methods. Of the total 114 patients fulfilling American–European Consensus Group (AECG) criteria for PSS 104 were included in the study and assessed by rheumatologists at T (time) = 0 months and T = 12 months. On each occasion, damage and activity data, and autoantibody status were collected. SF-36 and Profile of Fatigue and Discomfort-Sicca Symptoms Inventory (PROFAD-SSI) questionnaires were completed. Cross-sectional analysis of this data was subject to a process of expert validation by 11 ophthalmologists, 14 oral medicine specialists and 8 rheumatologists. Items were removed from the index if ≥ 50% of respondents recommended exclusion. Statistical validation was performed on remaining items. Spearman's rank analysis was used to investigate associations between damage scores and other disease status measures and Wilcoxon matched-pair analysis to assess sensitivity to change in the damage score. Results. Based on the expert validation, a 29-item damage score was agreed incorporating ocular, oral and systemic domains. Total damage score correlated with disease duration at study entry (r = 0.436; P < 0.001), physical function as measured by SF-36 (r = 0.250, T = 0 months; r = 0.261 T = 12 months) and activity as measured by the Sjögren's Systemic Clinical Activity Index (r = 0.213, T = 0 months; r = 0.215, T =12 months). Ocular damage score correlated with the ‘eye dry’ domain of PROFAD-SSI (r = 0.228, T = 0 months; r = 0.365, T = 12 months). Other associations not present on both assessments were considered clinically insignificant. On Wilcoxon analysis, the index was sensitive to change over 12 months (z = −3.262; P < 0.01). Conclusion. This study begins validation of a tool for collection of longitudinal damage data in PSS. We recommend further trial in both the experimental and clinical environment.