Short summary
Background
Aim of this subtask was to validate the Disease Activity Score of 28 Joints using ESR (DAS28-ESR) and CRP (DAS28-CRP), the Simplified Disease Activity Index (SDAI), and the Clinical Disease Activity Index (CDAI) used in rheumatoid arthritis (RA) for SSc patients.
Methods
Seventy-seven SSc patients, 40 RA patients, 20 patients with primary Raynaud’s syndrome (PR), and 28 healthy volunteers were assessed. Besides the DAIs, the European Scleroderma Study Group Activity Index (EScSG-AI), the HAQ-DI, the Cochin Hand Function Scale (CHFS) and the Short Form Health Survey (SF36) were evaluated. The validation procedure included the assessment for truth, discrimination and feasibility.
Results
DAS28-ESR, DAS28-CRP, SDAI and CDAI showed significant correlation with EScSG-AI, HAQ-DI, CHFS, and the physical component of SF36 (p<0.001). All four indices discriminated patients with SSc from RA, PR and healthy controls, respectively (p<0.01). With the exception of DAS28-CRP, the other three indices also discriminated between subgroups of SSc based on value of EScSG-AI (≤3 and >3) (p<0.05). All four DAIs showed a good inter- and intraobserver reliability based on repeated measures of two independent investigators (p<0.001).
Conclusion
All four disease activity composite indices were found to be valid measures for assessing arthritis in SSc. DAS28-ESR showed the best performance regarding reliability and construct validity.