Acute exacerbation of idiopathic pulmonary fibrosis: usual interstitial pneumonitis vs. possible usual interstitial pneumonitis pattern

Background: The prognosis of acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is very poor with a high mortality. The aim of this study was to describe the clinical features and survival of patients with AE-IPF with usual pulmonary fibrosis (UIP) and possible UIP (P-UIP) pattern on chest high resolution computed tomography (HRCT).Methods: This retrospective study included 107 patients with AE-IPF admitted to Nanjing Drum Tower Hospital from January 2010 to December 2016. The subjects were divided into UIP (n = 86) and P-UIP group (n = 21) based on chest HRCT. Continuous variables were analyzed using Student’st test or Mann-WhitneyU test. Categorical variables were analyzed usingχ2 test. Log-rank test was used for the survival analysis. Cox proportional models evaluated the risk factors for AE occurrence and survival.Results: The male, older patients, previous N-acetylcysteine use, elevated white blood cell (WBC) counts, and microbiology infection were more common in the UIP group than the P-UIP group (χ2= 13.567,P < 0.001;z = -2.936,P = 0.003;χ2 = 5.901,P = 0.015;t = 2.048,P = 0.043;χ2 = 10.297,P = 0.036, respectively). The percentage of AE with UIP pattern in idiopathic interstitial pneumonia (IIP) was significantly higher than P-UIP pattern (χ2 = 40.011,P < 0.001). Smoking was the risk factor for AE within 6 months after IPF diagnosis in the UIP group. The cumulative proportion survival of 30-days was significantly higher in the UIP group compared with the P-UIP group (χ2 = 5.489,P = 0.019) despite of the similar overall survival in the two groups. Multivariate Cox regression analysis indicated WBC count, partial pressure of oxygen in artery (PaO2)/fractional concentration of inspired oxygen (FiO2), and computed tomography (CT) score were the independent predictors for survival in the UIP group (hazard ratio [HR]: 1.070, 95% confidential interval [CI]: 1.027-1.114,P = 0.001; HR: 0.992, 95% CI: 0.986–0.997,P = 0.002; and HR: 1.649, 95% CI: 1.253–2.171,P < 0.001, respectively).Conclusions: AE occurrence of UIP patients in IIP was significantly more than P-UIP cases. The short-term survival was better in the UIP group despite of the similar overall survival in the two groups. WBC count, PaO2/FiO2, and CT score were the independent predictors for survival in UIP subjects.