Maxime Verhoeven

187 Development and validation of DAS-OST INTRODUCTION Rheumatoid arthritis (RA) is a common chronic inflammatory disease, mainly affecting joints and surrounding tissues. The disease requires life-long treatment, preferably according to tight-control and treat-to-target principles. Such treatment strategies require that patients frequently (in early disease or with active disease every 1-3 months) visit their physician for evaluation of medication effects, adverse events and disease activity. 1 Disease activity is typically measured by a combination of parameters, including a swollen and tender joint count (e.g., assessing 28 joints, SJC28/TJC28), C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) and an assessment of patient and/or physician of disease activity or general health typically using a visual analogue scale (VAS). These variables are often combined into an index like the disease activity score (e.g., DAS28). 2 However, this method of assessing disease activity is time consuming, especially given the busy out-patient-clinics and limited time per patient that rheumatologists have nowadays. Also to assess the joints for swelling and tenderness as objectively as possible, training and standardisation of joint examinations would be needed. 3–5 Therefore a tool assessing disease activity quickly, easily and objectively could be highly useful. The HandScan is a tool which measures within 5 minutes inflammation of wrist and small hand joints (i.e., MCP, (P)IP), using optical spectral transmission (OST-score). 6 Importantly a HandScan measurement can be performed by a non-health professional. 7 This procedure is more objective, and less painful than joint count assessment. The correlation between DAS28 and the OST-score (range 0-66=worst) is only moderate. 8 This may not be surprising as RA disease activity is a multifaceted construct. This is reflected by the fact that patient VAS as well as CRP/ESR are part of validated disease activity indices like DAS28, while the OST-score is a substitute of the swollen joint count only. In line with this, the correlation coefficient (ρ) of OST-score with SJC28 was found to be slightly higher (ρ=0.50) than with DAS28 (ρ=0.42). 8 Although the HandScan may be a substitution for joint count assessment only, this substitution may be beneficial, given its benefits, described above. The current study aimed to develop and validate an index for assessing RA disease activity (states) using the OST-score and other disease activity parameters, and to determine the agreement of this index with DAS28 and its accuracy in estimating remission, low (L) and high (H) disease activity (DA). 10