The serum level of GDF-15 in AE-IPF patients (1,279.22 ± 540.02 pg/ml) was significantly elevated compared with S-IPF subjects (891.30 ± 479.90 pg/ml) or HCs (107.82 ± 14.21 pg/ml) (p < 0.001 and p < 0.001, respectively) (Figure 1A). The gene discussed is GDF15; the disease is idiopathic pulmonary fibrosis.