Heterogeneity of Incidence and Outcome of Acute Exacerbation in Idiopathic Interstitial Pneumonia

Background And Objective: Acute exacerbations (AEs) of idiopathic pulmonary fibrosis (IPF) and other idiopathic interstitial pneumonia (IIP) have a poor prognosis. This study aims to clarify the incidence and prognosis of AE in IPF and the other IIP.

Methods: A total of 229 patients were enrolled, of whom 92 had IPF and 137 had 'IIP other than IPF' based on the American Thoracic Society/European Respiratory Society/Japanese Respiratory Society/Latin American Thoracic Association (ATS/ERS/JRS/ALAT) 2011 IPF Guidelines. IIP other than IPF included 11 patients with a surgical lung biopsy (SLB) and the remainder without such a biopsy. IIP other than IPF was further classified into IIP with a 'possible usual interstitial pneumonia (UIP)' pattern on HRCT (n = 75) and IIP with 'inconsistent with UIP' pattern (n = 62) based on published guidelines. Predictors of AE and the prognosis after AE were examined in these groups.

Results: The 1-year incidence of AE in IPF, IIP with possible UIP HRCT patterns and IIP with inconsistent with UIP HRCT patterns was 16.5%, 8.9% and 4.0%, respectively. AE occurred significantly more frequently in IPF than in IIP with possible UIP and inconsistent with UIP HRCT patterns after adjustment for BMI, modified Medical Research Council score and %forced vital capacity. Prognosis of AE-IIP with possible UIP HRCT pattern was significantly worse than that of AE-IPF.

Conclusion: Although AE occurred significantly less frequently in IIP with possible UIP and inconsistent with UIP HRCT patterns than in IPF, the prognosis of AE-IIP with possible UIP HRCT patterns might be worse than that of AE-IPF.