FLG and rheumatoid arthritis: After studying a large series of patients with various rheumatic conditions together with healthy controls, we concluded that anti-chimeric α-fibrin-filaggrin citrullinated peptide antibodies (anti-CFFCP) have a comparable sensitivity and specificity for RA compared to the gold standard commercial CCP2 test, and specifically, the CFFCP1 peptide ([Cit630]αfibrin(617-631)-S306,S319cyclo [Cys306,319, Cit312]filaggrin(304-324)) yielded better results in terms of identifying patients with poor radiographic outcomes [19].