Fig. 1

Proportion of ACPA-negative RA patients at different ages of RA onset. Proportion of ACPA-negative and ACPA-positive RA patients within the different age groups at RA onset in the five different cohorts. Number of patients in each age group: Leiden EAC: <25, n = 48; 25–29, n = 23; 30–34, n = 49; 35–39, n = 65; 40–44, n = 86; 45–49, n = 121; 50–54, n = 125; 55–59, n = 144; 60–64, n = 153; 65–69, n = 122; 70–74, n = 131; 75–79, n = 92; ≥80, n = 49; BARFOT: <25, n = 16; 25–29, n = 25; 30–34, n = 42; 35–39, n = 40; 40–44, n = 45; 45–49, n = 66; 50–54, n = 92; 55–59, n = 90; 60–64, n = 75; 65–69, n = 92; 70–74, n = 82; 75–79, n = 66; ≥80, n = 29; ESPOIR: <25, n = 30; 25–29, n = 24; 30–34, n = 45; 35–39, n = 52; 40–44, n = 65; 45–49, n = 78; 50–54, n = 107; 55–59, n = 109; 60–64, n = 73; ≥65, n = 49; Umeå: <25, n = 20; 25–29, n = 13; 30–34, n = 22; 35–39, n = 28; 40–44, n = 28; 45–49, n = 43; 50–54, n = 62; 55–59, n = 60; 60–64, n = 72; 65–69, n = 48; 70–74, n = 32; ≥75, n = 31; Lund: <25, n = 2; 25–29, n = 6; 30–34, n = 2; 35–39, n = 13; 40–44, n = 15; 45–49, n = 30; 50–54, n = 21; 55–59, n = 25; 60–64, n = 11; ≥65, n = 17. ACPA anti-citrullinated protein antibodies