Maxime Verhoeven

205 DAS28 vs. DAS-OST; rheumatologist’s clinical classification INTRODUCTION In rheumatoid arthritis (RA), life-long treatment according to the tight-control and treat- to-target principle is preferred, requiring frequent out-patient-clinic visits and contacts with rheumatologists. 1 Then, disease activity is usually assessed with DAS28, 2 a time consuming and partly subjective method. Moreover, training/standardisation of joint examinations, preferably yearly, is required to assess joints for swelling and tenderness as objectively as possible. 3–6 The HandScan is a medical device measuring inflammation in both hand and wrists using optical spectral transmission (OST, score 0 to 66=worse). The OST-assessment takes 5 minutes without much involvement of a health professional. 7 Some patients experience joint count assessments as painful, but the HandScan measurement is unpainful, an additional advantage. Recently, to quickly assess disease activity in RA, using DAS28-ESR as reference, we developed and validated an index consisting of the OST-score, gender, erythrocyte sedimentation rate (ESR), and patients’ general health on a visual analogue scale (VAS GH). This modification of DAS28, with OST-score replacing joint counts, was named DAS-OST. 8 Its formula is -0.44 + OST-score*0.03 + male sex*-0.11 + LN(ESR)*0.77 + VAS GH*0.03, and its explained variance in the external validation cohort was 71%, using DAS28-ESR as reference. To define remission (i.e., DAS28≤2.6) DAS-OST had an area under the receiver operating characteristic curve (AU-ROC) of 0.95 (95%CI 0.91-0.98); sensitivity was 79%, specificity 92%, and accuracy 88%. In the tight-control and treat-to-target principles, the decision whether RA is active or not is paramount. If there would be a tool to classify RA into active or inactive, the outpatients’ contacts with the rheumatologist might be limited to patients with active RA and/or medical problems. 1 The aim of this study was establishing the value of DAS-OST, versus that of DAS28, to classify RA as active versus inactive, with the rheumatologist’s clinical classification as active/inactive as reference standard, which is more comprehensive than disease activity indices alone. 9 METHODS This is a single center (Máxima MC Eindhoven; MMC) study, using routinely collected data from electronic medical records. The institutional ethical review board of MMC confirmed that the Medical Research Involving Human Subject Act (WMO) was not applicable to the protocol of this study (N19.002). 11