HMOX1 and idiopathic interstitial pneumonia: The purposes of the present research were to evaluate the utility of serum HO-1 for detection of AE in patients with each subtype, including secondary interstitial pneumonias (SIPs), as well as idiopathic interstitial pneumonias (IIPs), including the previously reported validation, and to compare detectability to other biomarkers commonly used in clinical practice.