Synovial tissue derived characteristics are included in a nomogram for the prediction of treatment response in naïve Rheumatoid Arthritis.

OBJECTIVES: This study aims to apply the synovitis assessment in routine care of naïve Rheumatoid Arthritis (RA) and to develop a multiparametric nomogram for baseline diagnostic and treatment response prediction.

METHODS: 1015 patients [545 RA, 167 Psoriatic Arthritis (PsA), 199 Undifferentiated Peripheral Inflammatory Arthritis (UPIA), 18 crystal arthritis, 26 connective tissue diseases and 60 osteoarthritis (OA)] undergoing ultrasound (US)-guided synovial tissue (ST) biopsy were enrolled (SYNGem) and stratified based on disease phase. The Krenn synovitis score(KSS) was assessed and integrated with disease characteristics and clinical outcome and a nomogram was created incorporating predictors of "DAS-Remission achievement at 6 months" in naïve RA treated with a treat to target strategy.

RESULTS: KSS significantly differs among patients with RA, as well as PsA and UPIA, when compared to OA. In RA, KSS directly correlated with DAS28 and was related to autoantibody positivity in naïve RA. Moreover, naïve RA achieving 6 months DAS-remission had, at baseline, lower KSS, shorter symptoms duration (VERA) and lower disease activity than naïve RA not achieving DAS-remission. On logistic regression, being VERA, not having high disease activity and having a KSS<5 at baseline, were synergistic factors of DAS-remission achievement at 6 months and a nomogram integrating baseline clinical and histological characteristics of naïve RA enabled to predict up to 81.7% of probability to achieve 6 months DAS-remission.

CONCLUSION: KSS is a reliable tool for synovitis assessment on US-guided ST biopsies being contingent on disease phase, autoimmune profile and integrated within a therapeutic response predictive nomogram in naïve RA.