Acute exacerbations of fibrosing interstitial lung disease associated with connective tissue diseases: a population-based study

BACKGROUND: Acute exacerbation (AE) is the major cause of morbidity and mortality in patients with idiopathic pulmonary fibrosis (IPF). AEs also occur in other forms of fibrosing interstitial lung disease (fILD). The clinical features and prognosis of AE patients with connective tissue diseases (CTDs) associated-ILD has not been fully described. METHODS: We retrospectively reviewed 177 patients with either IPF or a characterized CTD-ILD admitted to Nanjing Drum Tower Hospital with an AE from January 2010 to December 2016. RESULTS: The study cohort included 107 subjects with AE-IPF and 70 cases with AE-CTD-ILD. Female gender, prior use of corticosteroid and immunosupressants, lower serum albumin, higher D-dimer level, TLC% pred, survival, and treatment with immunosupressants and caspofungin were more common in the CTD-ILD group (all p<0.05). The incidences of AE-CTD-ILD and AE-IPF were similar in our single center (p = 0.526). TLC% pred was the risk factor for AE after ILD diagnosis for 1 year in CTD patients (p = 0.018). Log-rank tests showed patients with CTD-ILD had a significantly lower mortality rate compared with IPF patients after AEs (p = 0.029). No significant difference in survival was noted among CTD subgroups (p = 0.353). The survival was negatively correlated with WBC count, LDH and CT score, (p = 0.006, p = 0.013 and p = 0.035, respectively), and positively correlated with PaO(2)/FiO(2) ratio (p<0.001) in the CTD-ILD group. WBC count and PO(2)/FiO(2) ratio were the independent predictors for survival in AE-CTD-ILD after adjusting for other clinical variates in Cox regression Models (p = 0.038 and p < 0.001, respectively). CONCLUSIONS: The clinical characteristics of patients with AE-CTD-ILD differed from those with AE-IPF, while AE incidences were similar between the two groups. Subjects with AE-CTD-fILD tended to have a better prognosis, and WBC count and PO(2)/FiO(2) ratio were the independent survival predictors for these patients.