FBL and arthritic joint disease: Secondary objectives were to determine whether the anti-carbamylated fibrinogen (ACa-Fib) antibody response was specific and different to anti-cyclic citrullinated peptide (anti-CCP) antibody response, in other words, to study the cross-reactivity between ACa-Fib and anti-citrullinated fibrinogen antibodies, and to evaluate their prognostic value in the Very Early Arthritis (VErA) cohort.