In the stratified analysis by ACPA status, pooled associations were found between ACPA+ RA risk and IL-21 rs6822844 polymorphism in the homozygote comparison (OR = 0.54, 95% CI = 0.36–0.82, Pheterogeneity=0.786, P=0.004, Figure 6) and the recessive genetic model (OR = 0.52, 95% CI = 0.34–0.78, Pheterogeneity=0.454, P=0.002) (Table 2). Here, PRTN3 is linked to rheumatoid arthritis.