In addition, the ACPA titer of RA-ILD in China group (WMD = 380.30 (IU/mL), 95% CI: 137.31–623.29; P = 0.002) was higher than that of foreign group (WMD = 136.99 (IU/mL), 95% CI: 101.64–172.34; P < 0.00001) (Fig 14). The gene discussed is PRTN3; the disease is rheumatoid arthritis.