The associations between sialylated anti-cyclic citrullinated peptide (anti-CCP) antibodies bearing α-2,6-sialic acid (SIA), ST6Gal1 and Neu1 enzymes, and clinical disease activity measures such as disease activity score 28 (DAS28), the Simplified Disease Activity Index (SDAI), and Clinical Disease Activity Index (CDAI) are unknown in rheumatoid arthritis (RA). Here, ST6GAL1 is linked to rheumatoid arthritis.