Table 3.

Result of multiple linear regression analysis

	PSI#4		PSI#9		PSI#13		Postoperative death
	R 2	p value	R 2	p value	R 2	p value	R 2	p value
	0.365	p < 0.01	0.129	p < 0.01	0.111	p < 0.01	0.406	p < 0.01
Valuables	Coefficient	p value	Coefficient	p value	Coefficient	p value	Coefficient	p value
Intercept		n.s.		p < 0.01		n.s.		p < 0.05
Age	0.374	p < 0.01	-0.229	p < 0.01	0.018	n.s.	0.183	p < 0.01
Charlson comorbidity index	0.160	p < 0.01	0.116	n.s.	0.106	n.s.	0.285	p < 0.01
Difficulty of surgery	-0.233	p < 0.01	-0.152	p < 0.05	0.016	n.s.	-0.437	p < 0.01
Surgical volume	-0.191	p < 0.01	0.168	p < 0.05	0.314	p < 0.01	-0.065	n.s.

Multiple linear regression analysis was used for statistical analysis.