The prognostic value of IgA anti-citrullinated protein antibodies and rheumatoid factor in an early arthritis population with a treat-to-target approach

Heutz, J.W.; Looijen, A.E.M.; Kuijpers, J.H.S.A.M.; Schreurs, M.W.J.; Helm-van Mil, A.H.M. van der; Jong, P.H.P. de (2024)

Article / Letter to editor

The mucosal origin hypothesis of rheumatoid arthritis has renewed the interest in IgA autoantibodies, but their added value over IgG anti-citrullinated protein antibody (ACPA) and IgM rheumatoid factor (RF) for modern treatment outcomes remains unknown. We aimed to investigate the prognostic value of IgA-ACPA and IgA-RF for treatment outcomes in an early arthritis population. IgA-ACPA/RF isotypes were measured in baseline sera from 480 inflammatory arthritis (IA) patients, who were included in the treatment in the Rotterdam Early Arthritis Cohort trial (tREACH). The tREACH trial was a multicentre, stratified, single-blinded trial with a treat-to-target approach. The prognostic value of IgA-ACPA/RF was determined by evaluating differences in (1) quick-attained (< 6 months after diagnosis) and persistent remission rates, (2) DMARD-free remission and (3) biological use between IA patients with and without IgA-ACPA/RF over 3 years of follow-up. IgA-ACPA was present in 23% of patients and overlapped with IgG-ACPA positivity in 94%. Similarly, IgA-RF overlapped with IgM-RF in 90% of patients. IgA-ACPA positivity was associated with lower DFR rates and more biological use, but this effect was largely mediated by the presence of IgG-ACPA, since this effect disappeared after stratification for IgG-ACPA (HR 0.6, 95%CI 0.2-1.6 for DFR). No differences were observed in ‘quick-attained and persistent remission’ rates and for IgA-RF. Their seems to be no additional value of IgA-ACPA and IgA-RF for modern, long-term clinical outcomes. The effects of IgA-ACPA seen in our study are largely mediated by the presence of IgG-ACPA. Based on these results, there is no rationale for measuring these isotypes in daily practice.

• IgA autoantibodies
• Rheumatoid arthritis
• Anti-citrullinated protein antibody
• DMARD-free remission

• All authors: Heutz, J.W.; Looijen, A.E.M.; Kuijpers, J.H.S.A.M.; Schreurs, M.W.J.; Helm-van Mil, A.H.M. van der; Jong, P.H.P. de
• Date: 2024-07-03
• Journal: Immunologic Research
• Pages: 1 - 5
• DOI: doi:10.1007/s12026-024-09500-w
• Link: https://link.springer.com/article/10.1007/s12026-024-09500-w