PRTN3 and Arthritis: CSA patients will be enrolled in this trial irrespective of the auto-antibody status as it has been reported that with current treatment strategies, the disease burden is similar in ACPA-positive and ACPA-negative RA patients [19], and in addition, EULAR recommendations for the management of early arthritis recommend MTX as the first-line therapy, independent of the auto-antibody status [20].