In addition, the PCA revealed that the serum levels of eight proteins (IL–18, 4E–BP1, sHGF, IL–8, CCL20, sIL–10RB, sOPG and caspase 8; Figure 1) can distinguish patients in the high and low cumulative GC dose groups within the active RA group. The gene discussed is CXCL8; the disease is rheumatoid arthritis.