SMAD4 and rheumatoid arthritis: Among the 30 hub genes, 12 genes (BPTF, PHC2, JUN, KRAS, PTEN, FGFR2, ALB, SERB-1, SKP2, TUBA1A, IMP3, and SMAD4), which had AUC above 0.70 were appraised as biomarker genes, because they can distinguish RA patients in a more specific and sensitive manner (Figure 11).