BAL concentrations of KL‐6 were lower in patients with IPF than in those with non‐IPF (p = 0.0023, Figure 4a), while serum concentrations of KL‐6 were higher in patients with IPF than in the non‐IPF group (p = 0.0294, Figure 4b). Here, MUC1 is linked to idiopathic interstitial pneumonia.