Heterogeneity of incidence and outcome of acute exacerbation in idiopathic interstitial pneumonia

Background and objectiveAcute 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. MethodsA 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. ResultsThe 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. ConclusionAlthough 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. Acute exacerbations of idiopathic interstitial pneumonia occur significantly less frequently in patients with possible usual interstitial pneumonia (UIP)' and inconsistent with UIP' HRCT patterns than in idiopathic pulmonary fibrosis (IPF); however, the prognosis of exacerbations in patients with possible UIP HRCT patterns might be worse than that of IPF.