POS0477 HIGH DISEASE ACTIVITY AT BASELINE AND SEROPOSITIVITY ARE ASSOCIATED WITH TREATMENT RESPONSE AT ONE YEAR POST SYNOVIAL BIOPSY IN RHEUMATOID ARTHRITIS PATIENTS
Authors: K. Murray, C. Low, F. Young, M. Bienicka, E. Mylod, U. Fearon, D. Veale
Journal: Annals of the Rheumatic Diseases (2021)

Background: Despite recent therapeutic advances, our ability to predict prognosis and therapeutic response in RA remains imprecise. Objectives: To determine biomarkers predictive of outcome at one year following arthroscopy. Methods: RA patients were prospectively recruited and underwent knee arthroscopy performed under local anaesthetic. Each patient underwent a careful systematic assessment of demographic, clinical, and serologic factors on the day of arthroscopy and were reviewed at 2 weeks, 3, 6 and 12 months post arthroscopy. Erosive disease was defined based on plain-film radiographs of hands and feet. Disease activity at one year was used to define treatment response into responders (moderate/good EULAR Response) and non-responders. Clinical characteristics, synovial tissue cell profiles and immunohistochemistry were analysed for T Cells (CD3), B Cells (CD20, CD138), macrophages (CD68) and vascularity (Factor VIII) to establish predictors of treatment response. All areas of each biopsy section were examined and the sub-lining layer independently scored by 2 observers using a well-validated semiquantitative scoring method, ranging from 0 to 4 (0=no staining, 1=&lt;25%, 2=25–49%, 3=50–74%, and 4=75–100% staining). Factor 8 was scored by calculating the mean count of stained blood vessels per high-power field (at 20X magnification). Results: There were no significant differences between responders and non-responders regarding gender, age, disease duration, medications, erosive status, ESR, CRP or synovitis or vascularity at arthroscopy (Table 1). Interestingly, rates of RF and ACPA positivity, tender and swollen joint counts, DAS28 and DAS28CRP were all higher amongst treatment responders. Immunohistochemistry was a very poor predictor of treatment response. There were no significant differences between the two groups in CD3, CD20, CD138, CD68 or Factor 8 score. Table 1. Baseline Characteristics Responder (n=30) Non-responder (n=18) p value Female 20 (66.7%) 14 (77.8%) NS Age 51.5 (11.2) 54.2 (10.9) NS Disease duration 0.5 (0-16) 0.5 (0-10) NS RF positive 22 (73.3%) 5 (27.8%) 0.003 ACPA positive 22 (73.3%) 8 (44.4%) 0.045 Erosions 8 (26.7%) 5 (27.8%) NS Medications No DMARD 23 (76.7%) 10 (55.6%) NS csDMARD only 4 (13.3%) 3 (16.7%) NS TNFi 2 (6.7%) 3 (16.7%) NS Other bDMARD 1 (3.3%) 2 (11.1%) NS Patient global health, VAS (mm) 54.2 (10-100) 51.5 (0-90) NS SJC (28 Joints) 4.5 (0-16) 1 (0-18) 0.001 TJC (28 Joints) 7 (1-25) 1 (0-15) 0.001 ESR, mm/hr 23 (2-120) 24 (2-81) NS CRP, mg/L 5 (1-95) 6.5 (1-64) NS DAS28 5.01 (1.95-7.36) 3.93 (1.40-6.62) 0.003 DAS28CRP 4.78 (2.82-7.13) 3.39 (1.21-6.26) 0.002 Synovitis, VAS 65 (10-100) 70 (30-100) NS Vascularity, VAS 60 (10-90) 70 (30-100) NS Conclusion: In this small study, seropositivity and disease activity were higher in responders. Baseline immunohistochemical staining was not a good discriminator of treatment respons Disclosure of Interests: Kieran Murray Grant/research support from: Bresnihan Molloy and Newman fellowships, Candice Low: None declared, Francis Young: None declared, Monika Bienicka: None declared, EImear Mylod: None declared, Ursula Fearon: None declared, Douglas Veale: None declared