HMOX1 and idiopathic pulmonary fibrosis: Among patients with IPF, the median serum HO-1 level in patients having an AE was 59.1 ng/mL; this value was significantly higher than those in patients not having an AE (19.0 ng/mL, p < 0.001) and in control subjects (31.7 ng/mL, p < 0.001) (Figure 1(b)).