This study evaluated the prevalence, longitudinal evolution, and prognostic value of anti-carbamylated fibrinogen antibodies (ACa-Fib) of IgG and IgA isotypes in 575 early RA patients from the French ESPOIR cohort, measured at baseline, 6, and 24 months, compared against anti-CCP and RF.
ACa-Fib IgG was detected in 16.6% and IgA in 6.3% of anti-CCP-negative RA patients. The highest quartile of ACa-Fib IgG (≥20.29 AU) was linked to rapid radiographic progression (p=0.004), and ACa-Fib IgA (≥3.07 AU) independently associated with structural progression (OR=1.9, 95% CI 1.1–3.4, p=0.031); neither isotype predicted therapeutic response or remission.
In-house ELISA assays limit cross-center reproducibility. The cohort is single-country (French), which may restrict generalizability. No comparison to established anti-CarP assays beyond ACa-Fib is provided.
In early RA patients who are anti-CCP negative, testing for ACa-Fib IgG and IgA may help identify those at higher risk for rapid joint damage. Clinicians should consider these isotypes as complementary biomarkers when stratifying structural progression risk, particularly in smokers.
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