Pasw statistics software version 17

A chi-squared test was used to compare the nominal variable. Continuous variables were presented as mean and standard deviation. Between-group comparisons were performed using a chi-squared test or a Fisher’s exact test to compare the nominal variables and one-way analysis of variance test to compare the continuous variable. To determine the independent mortality variables, a multivariate analysis was used to evaluate the association with age, BMI, comorbidities, the mMRC scale, postbronchodilator FEV₁, and exacerbation history in the preceding year. The ability of the GOLD 2017 to predict exacerbations and all-cause and respiratory mortality was evaluated using a logistic regression analysis with receiver operating characteristic (ROC) curve estimations and an intramodal area under the ROC curve (AUC) comparisons, and P<0.05 was considered statistically significant. Statistical analyses were performed by using the PASW statistics software version 17.0.2 (SPSS Inc., Chicago, IL, USA).