2.5 Statistical analysis
Data were processed using the Statistical Package for the Social Sciences 28 (SPSS) program. Categorical data are presented as numbers and frequency, continuous data as means with standard deviation or as medians with interquartile range (IQR). The Kolmogorov-Smirnov test was used to test the normality of distribution of variables. Categorical data were compared using the chi-squared test or Fischer’s exact test, and continuous data using the Student’s t-test or Mann-Whitney U-test. Receiver operating characteristic (ROC) analysis was performed to determine cut-off values for the diameters of FO and VSD to predict urgent BAS. After univariate analysis with possible factors thought to be associated with urgent BAS, variables that were significantly related to urgent BAS in univariate analysis and other factors that may be associated with urgent BAS were included in the multivariate analysis. Hosmer–Lemeshow goodness of fit statistics was used to assess model fit. A P value of less than 0.05 was considered significant.