Causes of acute respiratory hospitalizations predict survival in fibrosing interstitial lung diseases.

Acute exacerbation of ILD (AE-ILD) is a common reason for hospitalization; it is also associated with significant mortality. Less is known about the prognostic significance of other events causing acute, non-elective hospitalizations in ILD patients. ILD patients hospitalized due to acute respiratory worsening were collected from medical records. Reasons for respiratory deterioration were classified into AE-ILDs and other causes. Clinical features and survival data of idiopathic pulmonary fibrosis (IPF) and other types of ILDs were evaluated and compared. In all, 237 patients (138 with IPF and 99 with other ILD) fulfilled the inclusion criteria. Of the non-IPF ILD types, the most prevalent subgroups were connective tissue disease-associated ILD (n = 33) and asbestosis (n = 22). The most common cause for hospitalization was AE-ILD explaining 41% of hospitalizations. Lower respiratory tract infection (22%), subacute progression of ILD (12%) and cardiovascular causes (7.2%) were other common reasons for hospital treatment. Patients with a lower respiratory tract infection had a more favorable prognosis compared with patients with AE-ILD. AE-ILDs were less fatal than cardiovascular or concurrent non-ILD-related causes for hospitalizations in non-IPF patients. High Gender-Age-Physiology (GAP) index was a marker for shortened survival and earlier AE-ILDs in all patients. IPF patients had a significantly shorter overall and post-hospitalization survival time compared with other ILDs. Most respiratory hospitalizations in ILD patients were related to causes other than AE-ILD, which highlights the importance of accurate differential diagnosis in order to target the appropriate treatment for each ILD patient.