Quantitative MRI tenosynovitis volume explains the association between tendon involvement and future development of clinical arthritis in anti-cyclic citrullinated peptide-positive at-risk individuals

OBJECTIVES: Tenosynovitis is a key imaging feature in the preclinical phase of rheumatoid arthritis. Prior studies suggest that presence of magnetic resonance imaging (MRI) tenosynovitis may better predict future clinical arthritis than MRI synovitis. We hypothesised that the volume of subclinical inflammation within tendon sheaths may explain this association in anti-cyclic citrullinated peptide (anti-CCP) positive at-risk individuals. This study sought to assess whether MRI-derived tenosynovitis (TSV) and joint synovitis (SV) volumes predict inflammatory arthritis (IA) in anti-CCP-positive individuals without clinical synovitis, beyond clinical/serological markers. METHODS: We included 223 anti-CCP-positive individuals with musculoskeletal symptoms without clinical synovitis. All underwent baseline contrast-enhanced MRI of the hand and wrist. TSV and SV were quantified via manual segmentation and three-dimensional (3D) reconstruction (OsiriX-MD). IA progression was defined as ≥1 clinically swollen joint. Cox regression and receiver operating characteristic (ROC) analyses were performed. RESULTS: Of 223 participants, 67 (30%) developed IA over a median 13.3-month follow-up. Inter-reader agreement for volumetric scoring was excellent (intraclass correlation coefficient > 0.90 across all regions). Baseline tenosynovitis (34.5%) was associated with progression (P < .001). TSV was higher in progressors than non-progressors (1607 vs 705 mm³, P = .003), remained predictive after adjusting for SV (P = .008), and outperformed SV in ROC analysis (area under curve (AUC) = 0.697 vs 0.582). In multivariable analysis, TSV (P < .001) and tender joint count (P = .014) independently predicted progression beyond clinical and serological markers. Higher total inflammation volume correlated with shorter time to progression (P = .008). CONCLUSIONS: MRI-derived TSV independently predicts IA and outperforms SV. Quantitative TSV assessment may enhance risk stratification and support preventive strategies in at-risk individuals.