Background Hand function can deteriorate dramatically due to joint involvement in rheumatoid arthritis (RA) and systemic sclerosis (SSc).¹ While there are valid tools for the assessment of synovitis in RA, there is no validated outcome measure for evaluating synovitis in SSc.²

Objectives To determine the validity of disease activity indices (the disease activity score of 28 joints [DAS28], the disease activity score of 28 joints using CRP [DAS28-CRP], the Simplified Disease Activity Index [SDAI], and the Clinical Disease Activity Index [CDAI]) developed for RA in patients with SSc.

Methods 77 patients, 27 with limited and 50 with diffuse cutaneous SSc, 40 RA patients, 20 with primary Raynaud's syndrome and 28 healthy volunteers were assessed. Besides the articular disease activity indices the European Scleroderma Study Group activity index (EScSG-AI), our recently developed modified scleroderma activity index (MSAI)³, the Health Assessment Questionnaire (HAQ), the Cochin Hand Function Scale (CHFS), the Quick Questionnaire of the Disability of the Hands, Arms and Shoulders (qDASH), and the Short Form Health Survey (SF36) were also evaluated.

The validity of the articular activity indices was assessed for truth, discrimination and feasibility. For statistical analysis Spearman-rank correlation, Mann-Whitney tests and intraclass correlation tests were used.

Results Based on physical examination of the 28 joints tenderness was found in 48%, swelling in 33% and contractures in 56% of the SSc patients. There was no significant difference in the number of contractures between patients with disease duration more or less than 4 years (p>0.05). In the SSc group DAS28, DAS28-CRP, SDAI and CDAI showed significant correlation with each other (p<0.001), and also correlated with EScSG-AI, MSAI (p<0.01), HAQ, qDASH (p<0.001), CHFS (p<0.01), and the physical component of SF36 (p<0.001) in the SSc group. All four indices discriminated between patients with SSc and RA (p<0.01), SSc and healthy controls (p<0.001). DAS28, SDAI and CDAI also discriminated between subgroups of SSc based on disease activity (EScSG-AI ≤3 vs >3) (p<0.05). All four indices discriminated between SSc subgroups based on values of HAQ (<1 vs ≥1) (p<0.01). All four indices showed good inter- and intraobserver reliability (p<0.001).

Conclusions DAS28, SDAI and CDAI were found to be valid measures for assessing articular disease activity in SSc. DAS28 and SDAI seem to be the most valuable tools among these. Limitation of the study was the relatively low number of patients with tender and/or swollen joints. Further investigations are needed for defining responsiveness of these indices.

References

1. Smolen, J.S. and D. Aletaha, Arthritis Res Ther, 2009. 11: p. 204.

2. Clements, P.J., et al., Semin Arthritis Rheum, 2012. 41: p. 801-14.

3. Minier, T. et al., Rheumatology (Oxford), 2010. 49: p. 1133-45.

Acknowledgements This study was supported by the Seventh Framework Program of European Commission as part of the DeSScipher Project (grant agreement No. 305495), Observational Trial 2.

Disclosure of Interest None declared