AK1 and rheumatoid arthritis: Specifically, 11 of the 27 autoantibodies were significantly correlated with CDAI in ACPA+ RA, with 6 (for PYGB, EXT2, CDKN2B, FAS, GNA15, and MMP2) being positively correlated, and 5 (for MED4, RAB38, PAK2, AK1, and PELO) being negatively correlated.