Autoantibodies to Joint‐Related Peptides Are Associated with Onset of Rheumatoid Arthritis in Presymptomatic Seronegative Individuals

OBJECTIVE: To identify autoantibodies in presymptomatic individuals that associate with the onset of rheumatoid arthritis (RA), and to distinguish early RA from osteoarthritis (OA), particularly in individuals lacking classic RA serological markers. METHODS: We analyzed serum and plasma from three cohorts: pre-symptomatic individuals who later developed RA (N=518), a subset of these at RA diagnosis (N=241), matched population controls (N=530), and OA patients (N=287). Bead-based multiplex flow immunoassay detected IgG autoantibodies against joint-related peptides relevant in arthritis models. Principal component analysis was used to identify subgroups and univariable regression analyses to characterise the performance of autoantibodies with significance for RA patients negative for anti-cyclic citrullinated peptide (anti-CCP) and rheumatoid factor (RF), i.e. the seronegative (SeNe) test. Multivariable logistic regression identified autoantibodies with strongest discriminative power between cases and controls. RESULTS: Autoantibody profiles revealed three distinct pre-symptomatic subgroups, suggesting early immune heterogeneity. The SeNe test was associated with symptom onset within 2.5 years in 13% of anti-CCP and RF-negative individuals. Specificity for RA versus OA was 97% (95% CI: 95-99%). An improved version (SeNe 2.0) identified 16% of anti-CCP and RF-negative pre-symptomatic individuals with 98% specificity versus population controls. Two of five SeNe 2.0 autoantibodies were associated with the pre-symptomatic state in the multivariable model including RF and anti-CCP. CONCLUSION: These novel biomarkers can identify pre-symptomatic, seronegative individuals at high risk of RA onset and support their recruitment into trials for personalised prevention. Additionally, they distinguish early seronegative RA from OA with high specificity.