Figure 10C shows the value of the four hub genes in the diagnosis of IPF in the training set. CXCL12, CTSG, and SPP1 were significantly upregulated in the IPF group, while CXCR2 was highly expressed in the normal group. Moreover, the AUROC values were 0.92 (95% CI = 0.86–0.97) (Figures 10D, H), 0.74 (95% CI = 0.64–0.85) (Figures 10E, H), 0.79 (95% CI = 0.70–0.88) (Figures 10F, H), and 0.71 (95% CI = 0.59–0.82) (Figures 10G, H). CXCL12 emerged as the gene most strongly associated with IPF. The gene discussed is CTSG; the disease is idiopathic pulmonary fibrosis.