Statistical analysis
SPSS17.0 software (SPSS IBM Inc., Chicago, IL, US) was used for
statistical analysis. Measurement data are here presented as mean ±
standard deviation (x̅ ± s). Normally distributed measurement data were
compared using paired t-test. Non-normally distributed measurement data
were compared using signed rank sum test of paired data, and comparison
of the count data was performed using chi-square test. Correlation
analysis was performed using logistic regression analysis. P< 0.05 was considered statistically significant.