Maxime Verhoeven

171 Utility of the HandScan in monitoring disease activity in RA INTRODUCTION The treatment of RA has significantly improved over the last decades due to earlier and more intensive treatment, with swift adjustment of treatment if the target is not achieved e.g., initiating biological (b) disease modifying anti-rheumatic drugs (DMARDs). 1,2 To treat RA patients effectively it is important to focus on achieving and maintaining remission (treat-to-target principle), thereby preventing or restricting joint damage. Therefore, patients visit the out-patient-clinic regularly to monitor disease activity (i.e., tight-control principle). 3,4 The disease activity score assessing 28 joints (DAS28) is widely used to evaluate disease activity also in individual patients. Joint tenderness and swelling of 28 joints, together with an acute phase reactant (erythrocyte sedimentation rate (ESR) or C-reactive protein) and a visual analogue scale (VAS) for patient’s experience of disease activity, are combined in the composite DAS28 measure. This method of evaluating disease activity, has a considerable inter and intra assessor variability, especially without formal training of assessors, is time consuming and partly subjective. 5 The HandScan, based on the principle of optical spectral transmission (OST), is a new method which has been developed to measure RA inflammation in hand (i.e., MCP1-5, IP1 and PIP 2-5) and wrist joints. The RA patient places both hands in the HandScan, and by using red/near-infrared light, the grade of inflammation is assessed per joint (i.e., individual joint score), as well as a total score of all included joints (i.e., total OST-score). A HandScan measurement can be performed at any location, if the device is available, within 5 minutes, without taking much time of a healthcare professional. 6 More detailed information is provided in Supplementary Data S1. In a cross-sectional study, the OST- score as provided by the HandScan (range 0-66=worst inflammation) was reproducible, and it correlated (coefficient=0.54) with the grade of inflammation of hand and wrist joints as assessed by ultrasonography. 7 The outcome of the HandScan was more sensitive in detecting subclinical disease activity (as determined by ultrasonography) than physical exam, and its assessment is less time consuming than that of DAS28. 8 In addition, the HandScan might facilitate early detection of response to treatment, typically assessed at 3 to 6 months after start of (added) therapy. This may be particularly relevant in (early) RA patients treated according to the tight-control principle, stepping up treatment to more intensive (biological) treatment modalities, for example, tumour necrosis factor inhibitors (TNFi). 2 All previous research with the HandScan was cross-sectional. However, in light of the treat-to-target principle, it is specifically important to establish if changes in OST- score are associated with changes in DAS28 (as reference standard) in individual RA patients (i.e., if a longitudinal association of OST-score with disease activity exists). Also, for optimal treat-to-target strategies, it would be valuable if the OST-score could predict 9