Maxime Verhoeven

172 Chapter 9 clinical response to treatment early after treatment initiation. Furthermore, during the last decades patient reported outcomes became of more interest as measure for the impact of disease, and therefore the relation of OST-score with individual components of DAS28, functional disability and quality of life of patients is also of interest. 9 The current explorative study aimed to determine the longitudinal association of the HandScan with DAS28 (i.e., are OST-score changes related to DAS28 changes) in individual RA patients, which, if present and strong enough, would provide a rationale for its use as a disease activity monitoring instrument like DAS28. In addition, the longitudinal association of OST-score with the swollen joint count (SJC), tender joint count (TJC), functional disability and quality of life of patients was determined. Furthermore, the ability of short-term (i.e., baseline to 1 month) OST-score changes to predict clinical response to conventional synthetic (cs)DMARDs or TNFi treatment at 3 or 6 months was studied. We hypothesized that a longitudinal association between OST-score and DAS28 exists. Furthermore, we hypothesized that short-term changes in OST-score can predict clinical response to treatment. METHODS This is an observational cohort study, among RA patients. The institutional review boards of the participating centres confirmed that the Medical Research Involving Human Subjects Act (WMO) was not applicable to this study, and all patients gave written informed consent. Consecutive early and established RA patients visiting the out-patient-clinic of participating centres, from April 1, 2017, to May 31, 2019, and satisfying the inclusion criteria were all eligible for inclusion. Inclusion criteria were: meeting the 2010 ACR/EULAR criteria, and age above 18 years. Early RA patients were further required to be DMARD- naïve and started DMARD therapy, usually a csDMARD like methotrexate, according to the tight-controlled treat-to-target principle. Established RA patients started with or switched to another TNFi because of active disease, also in a tight-controlled manner, as additional therapy. Exclusion criteria for both cohorts were rheumatic autoimmune disease other than RA or a current inflammatory joint disease other than RA (e.g., gout). Other exclusion criteria were glucocorticoid use <6 weeks prior to baseline for early RA and previous use of the same TNFi (i.e., restarting treatment) for established RA. All included patients visited the out-patient-clinic just before starting their (additional) treatment (baseline), and 1, 3 and 6 months thereafter (i.e., tight-controlled). In early RA patients the csDMARD dose (typically MTX start at 10 mg/week) was increased, if necessary, every month in steps of 5mg according to the treat-to-target principle. In established RA patients, the dose of the TNFi started was not modified during the study