Statistical analysis
The continuous variables are summarized as the means±SD, and categorical
variables as proportions. The differences between the patients with and
without preexisting anemia were examined with the use of Pearson
Chi-Square test or Fisher’s exact test for categorical variables, or
Student t-test or Mann-Whitney U test for continuous variables.
Univariate and multivariate logistic regression models were used to
determine the factors independently associated with the primary
endpoint. Likely parameters were included as explanatory variables in
the univariate models. For some continuous variables included in the
models, the cut-off points were determined according to their upper or
lower normal limits, otherwise, the medians. Variables with a P value of
<0.1 in the univariate analyses were further included in the
multivariate models. All statistical analyses were performed with the
use of JMP software version 13.0 (SAS Institute, Cary, NC, USA). A P
value of <0.05 was considered significant.