FRI0646 Synovial tissue histopathology findings in early ra. is it usefull? analysis of the belgian cap48 cohort

Background: The development of ultrasound-guided synovial biopsy will enable synovial tissue collection from small joints and will facilitate histopathological studies, thus improving the understanding of early rheumatoid arthritis (ERA). The CAP48 cohort is an original multicentre prospective observational study of early Rheumatoid Arthritis (RA) patients up to 50 years old supported by a charity program of the Belgian French speaking radio-television (RTBF). Objectives: The objectives of this cohort are to observe if a tight control favour remission at 6 months and to define synovial markers for severy and response to therapy. Methods: RA patients fulfilling the ACR/EULAR 2010 criteria and naive to DMARDs therapy were recruited. Synovial biopsies before treatment were obtained using an ultrasound guided needle biopsy (US-NB) of the small joints or miniarthroscopy of the knee. RA disease activity measures including DAS28CRP domains were evaluated every 3 months and treatment was adapted by the treating physician. Tissues were assessed for quality. Retrieved tissue was fixed, stained and paraffin embedded for blinded tissue pathotype description. Results: A synovial biopsy was performed in 37 patients using US-NB in n patients. Patients were classified according 4 types of synovial histopathology findings. Baseline characteristics of the cohort is summarized in table 1. All patients in the diffuse lymphoid group were ACPA negative and the majority of the ACPA positive patients were classified in the pauci immune and fibrous group. As shown in figure 1, the pauci immune ERA group showed lower DAS28-CRP response than the other groups. Conclusions: Synovial tissue analysis could provide a step change towards personalized medicine in daily clinical practice for disease stratification and treatment selection of ERA. In the CAP48 cohort, a high number of these young and ERA patients achieved remission at 6 months but a lower response was observed in the pauci immune group. Further analyses are ongoing to define individual synovial markers of severity and response. Disclosure of Interest: None declared