Fig. 2
Meta-analysis on the association between age of onset (<50 and >50 years) and the presence of ACPA, RF and anti-CarP. Association between ACPA (a), RF (b) and anti-CarP (c) with age of onset in the different cohorts. The meta-analysis summarizes the effect of age of onset in the different cohorts and is based on a random effect model, combining ORs from separate logistic regression analyses of the different cohorts with age and gender as independent variables and ACPA, RF or anti-CarP as outcome. Separate meta-analyses were performed for the association between autoantibodies and age <50 years and >50 years. OR of 0.96 indicates that for a 1-year increase in age, the odds of being ACPA-positive decrease 4%; this is 18% per 5-year increase in age of RA onset (0.965). ACPA anti-citrullinated protein antibodies, anti-CarP anti-carbamylated protein antibodies, OR odds ratio, RF rheumatoid factor