HMOX1 and idiopathic pulmonary fibrosis: Using the best cut-off value of serum HO-1 (41.8 ng/mL) for predicting 12-week mortality, we compared the clinical characteristics (Table 4) and survival curves (Fig. 3) between patients in the high- and low-serum HO-1 groups and found significant difference in serum HO-1 by log-rank test among all enrolled patients and in patients with IPF (P = 0.021, Fig. 3A; and 0.015, Fig. 3B, respectively).