Statistical analysis
SPSS statistical software (version 18.0; IBM Corp., Armonk, NY, USA) was used for data analysis. The chi-squared test was used to analyze the difference in count data between groups. An independent t-test was used to compare the measurement data if they had a normal distribution. The non-parametric Mann–Whitney U-test was used when the measurement data did not conform to a normal distribution using the Shapiro Wilk test. The calibration level was set at α=0.05.