Statistical analysis
Allanalysis were performed by using Statistical Package for the Social Sciences (SPSS, Version 22.0; SPSS, Chicago, III). Patients were divided into two groups according to SF status. T-test and Pearson χ2 test were used to compare variables between SF and non-SF groups. ROC Curve analysis was used for prediction levels of the nomograms. Statistical significance was accepted as p <0.05 for all analyses.