Jonsson MK, et al. - Authors evaluated the prevalence of baseline anti-citrullinated protein antibody (ACPA) reactivities in an inception cohort of patients with early rheumatoid arthritis (RA). They also gauged their associations with disease activity, treatment response, ultrasound findings and radiographic damage. At baseline, disease activity measures and ultrasound scores were lower in ACPA reactivity-positive vs ACPA reactivity-negative patients. In intensively treated and closely monitored early RA, the clinical relevance of analysing ACPA reactivities was limited without any apparent relationships with disease activity, prediction of treatment response or radiographic progression.