Fig. 4

ACPA level of ACPA-positive RA at different ages of RA onset; data from five cohorts. Association between age of onset and ACPA level within RA patients of the Leiden EAC (a), BARFOT (b), ESPOIR (c), Umeå (d) and Lund (e) cohorts. In Lund the upper detection limit of the anti-CCP2 test was 200 U/ml; there were 76 patients with anti-CCP2 level > 200 U/ml. Horizontal lines represent median values. Each dot represents one patient. ACPA anti-citrullinated protein antibodies