Statistical analysis
Continuous variables were analysed using the independent t-test or
Mann–Whitney U-test depending on the normality of the distribution.
Normality was examined by the use of the Shapiro–Wilk test. Categorical
variables were analysed by Pearson’s chi-squared test or Fisher’s exact
test, as appropriate. All statistical tests used a two-tailed α of
0.05.
A P value < 0.05 was considered statistically significant.
Analyses were performed using STATA 13.0 (StataCorp. Stata Statistical
Software: Release 13. CollegeStation, TX, USA).