OP0176 CHRONOLOGICAL ORDER OF DECREASE OF SYNOVITIS, OSTEITIS AND TENOSYNOVITIS IN ARTHRITIS PATIENTS RECEIVING FIRST DMARD-TREATMENT

Background:During the last decennium advanced imaging modalities have refined our understanding of the tissues involved in RA and have shown that not only joints but also bones and tendons can be inflamed at diagnosis. However, the time-order of decrease of these inflammatory features after initiation of DMARDs is unknown. Whether this differs for ACPA-positive and ACPA-negative patients is also unknown.Objectives:To achieve better understanding of the time order in which the different inflamed tissues (joint, tendon, bone) respond to DMARD-treatment and whether this differs between ACPA-subgroups.Methods:216 consecutive patients with early undifferentiated or rheumatoid arthritis, who received DMARD-treatment, were studied. Unilateral 1.5 Tesla contrast-enhanced MRIs of MCPs, wrists and MTPs were performed at baseline (before treatment) and after 4, 12 and 24 months. MRIs were scored for synovitis, osteitis and tenosynovitis in line with the RAMRIS, in known time-order but blinded for clinical data. Data of 4 serial time-points (three time intervals) were studied with autoregressive cross-lagged models. These models evaluated the influence of two time patterns in one model: 1) a simultaneous pattern (“extra change in one inflammatory feature was associated with extra change in another feature”) and 2) a subsequent pattern (“change in one inflammatory feature preceded change in another feature”). All analyses were repeated stratified for ACPA-status (anti-CCP2).Results:In all patients, all combinations of inflammatory features showed significant simultaneous decrease in all time intervals (0 – 4 /4 – 12/12 – 24 months; all pWhen considering ACPA-negative and ACPA-positive patients separately, similar results were obtained. In addition, in ACPA-positive patients, synovitis change between 4 - 12 months preceded osteitis change at 12 – 24 months (p = 0.002); this was significantly different from ACPA-negative patients (pConclusion:This study increased the understanding of the response to treatment on tissue level. In addition to simultaneous decrease of synovitis, osteitis and tenosynovitis, also time orders of inflammation decrease were identified. These differed between ACPA-subgroups, implying a different interaction of synovium and bone in these patients.Disclosure of Interests:None declared