Statistical Analysis
The database was established by EpiDate3.1 software, the data were input
twice in parallel. The final analysis database is formed after logical
error checking and sorting of the input data and analysis and processing
of outliers. Continuous variables were expressed as means ±SDs; if the
data conformed to a normal distribution, the two groups were compared
using an independent samples t test, and multiple groups were compared
using variance analysis. The least significant difference (LSD) was used
for pairwise comparisons among those with intragroup differences. For
nonnormally distributed data, Wilcoxon rank-sum tests were used for
comparisons between two groups, and Kruskal-Wallis H tests were used for
comparison between multiple groups. Categorical variables were described
as percentages (rates); comparisons between two groups were performed
using chi-square tests, and comparisons between multiple groups were
performed using crosstabulation analysis. After we created the
propensity score, patients were matched on the propensity score in a 1:2
ratio. We used calipers of width 0.2 of the standard deviation of the
logit of the propensity score, as recommended in literature. Balance
diagnostics were done by comparing the absolute standardized differences
of the propensity scores, with values greater than 0.1 indicative of
imbalance. P<0.05 was considered statistically significant.
All analyses were performed in SPSS version 23.