ASSOCIATIONS BETWEEN POWER DOPPLER ULTRASOUND FINDINGS AND B-MODE SYNOVITIS AND CLINICAL ARTHRITIS IN JUVENILE IDIOPATHIC ARTHRITIS USING A STANDARDIZED SCANNING APPROACH AND SCORING SYSTEM

N. K. Sande, V. Lilleby, A. B. Aga, E. Kirkhus, B. Flato, P. BøyesenOslo University Hospital, Department of Rheumatology, Oslo, Norway University of Oslo, Institute of Clinical Medicine, Oslo, Norway Oslo University Hospital, Department of Radiology, Oslo, Norway  Background Ultrasound is a valuable tool in the evaluation of synovitis in patients with juvenile idiopathic arthritis (JIA). However, interpretation of Doppler signals in children is challenging due to physiologic vascularization that can be misinterpreted as pathologic findings. Definitions for synovitis in children, including B-mode (BM) and Doppler findings, have been developed and emphasize that only Doppler signals within synovial hypertrophy should be considered as synovitis [1]. So far, few studies have implemented this definition in the evaluation of Doppler findings in children. Objectives To describe power Doppler (PD) ultrasound findings in joint regions with BM synovitis in patients with JIA using a standardized scanning protocol and scoring system. Further, to examine associations between PD findings and BM synovitis, clinical arthritis, patient characteristics and disease activity. Methods In this cross-sectional study one rheumatologist with broad ultrasound experience, blinded to clinical findings, performed ultrasound examinations in 27 patients with JIA aged 2 to 17 years old with suspected clinical arthritis using the same ultrasound machine with standardized settings. The elbow, wrist, metacarpophalangeal 2-3, proximal interphalangeal 2-3, knee, ankle and metatarsophalangeal 2-3 joints were assessed bilaterally and scored for BM and PD findings using a joint-specific scoring system (grades 0-3) with reference atlas [2]. Pathologic BM and PD findings were defined as grades ≥1. Multilevel mixed-effects ordered logistic regression models were used to explore associations between PD findings and BM synovitis, clinical arthritis, age, sex, JIA subgroup, disease duration and measures of disease activity (Juvenile Arthritis Disease Activity Score (JADAS10), (range 0-40). Results Overall, 971 joint regions were evaluated by ultrasound, 129 had BM synovitis and were assessed for PD. PD findings were detected in 45 joint regions (34.9%), most frequently in the lateral parapatellar recess of the knee joint (24.4%) (Figure 1). Increasing PD grades were associated with higher BM grades (OR=5.0, 95% CI: 2.7-9.1, p<0.001) and with the presence of clinical arthritis (OR=7.4, 95% CI: 2.7-21.7, p<0.001). PD findings were not associated with age, sex, JIA subgroups, disease duration or JADAS10. Conclusion Increasing severity of PD findings were significantly associated with BM synovitis and with the presence of clinical arthritis. These findings suggest that PD signals detected using a standardized ultrasound examination and scoring system can reflect active disease in patients with JIA. References Roth et al. Arthritis Care Res. 2017;69(8):1217-23. Sande et al. RMD Open. 2021;7(2):e001581. Image/graph:Figure 1. Illustration of variations in power Doppler (PD) ultrasound findings in two joint regions of the knee in a 10-year-old child with juvenile idiopathic arthritis (JIA). A: Longitudinal dorsal scan of the knee joint (suprapatellar recess) showing B-mode (BM) synovitis, B: and BM synovitis without abnormal PD signals (grade 0). C: Longitudinal dorsal scan of the knee joint (lateral parapatellar recess) showing BM synovitis, and D: BM synovitis with abnormal PD signals (grade 3). Acknowledgements: NIL. Disclosure of Interests Nina Krafft Sande: None declared, Vibke Lilleby: None declared, Anna-Birgitte Aga Speakers bureau: AbbVie, Eli Lilly, Novartis, Pfizer, Consultant of: AbbVie, Eli Lilly, Novartis, Pfizer, Eva Kirkhus: None declared, Berit Flato: None declared, Pernille Bøyesen: None declared. Keywords: Ultrasound, Imaging, Inflammatory arthritides DOI: 10.1136/annrheumdis-2023-eular.1294Citation: , volume 82, supplement 1, year 2023, page 672Session: Paediatric rheumatology (Poster View)