Statistics

Continuous numeric variables are expressed as mean with standard deviation and 95% confidence interval (CI) or median with range. Continuous variables were compared with Student’s t-test. Simple linear regression analysis was performed to obtain the regression equation, correlation coefficient (r), and coefficient of determination (R²). Spearman correlation coefficient (ρ [rho]) was used for correlation analysis. A p-value < 0.05 was considered to indicate a statistically significant difference. All statistical analyses were performed using SPSS version 22 (IBM Corp., Armonk, NY, USA) and MedCalc version 20.010 (MedCalc, Ostend, Belgium).