PADI4 and rheumatoid arthritis: According to the Mann‒Whitney test of significance in measuring the correlation between PAD4 and RA patient group characteristics, the analysis revealed that there was a significant difference between PAD4 levels and ACPA positive cases, with a p-value < 0.001; however, there was an insignificant difference between PAD4 and sex, family history and RF, with a p-value ≥ 0.05 (Table 6).