PRTN3 and rheumatoid arthritis: We included four ACPA positive groups with different characteristics, comprising an ACPA positive without joint complaints group (n = 95), an ACPA positive with joint complaints group (n = 83), both from Lifelines, an ACPA positive RA risk group (n = 28) and an ACPA positive early RA group (n = 33), to enable identifying differences in serum biomarkers associated with atherosclerosis.