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 .