ESR1 and rheumatoid arthritis: Spearman's rank order correlation test was performed to investigate the correlation between synovial TRAF6 expression and ESR, CRP, RF, ACPA, TJC in 28 joints, SJC in 28 joints, HAQ, morning stiffness, gripping power or DAS28-CRP, all of which are serological or clinical parameters that reflect disease activity or severity of RA.