Effect of transplant center volume on post-transplant survival in patients listed for simultaneous liver and kidney transplantation

Table 1 Characteristics of recipients of liver transplant alone or simultaneous liver-kidney transplant

Variable1	Cases missing data	Received LTA (n = 393)	Received SLK (n = 4187)	P value2
		Mean (SD) or n (%)	Mean (SD) or n (%)
Transplant center SLKT volume	0	107 (± 83)	91 (± 66)	< 0.001
Transplant center LTA volume3	0	1187 (628)	1111 (627)	0.024
Age (yr)	0	54.2 (± 9.7)	54.8 (± 9.6)	0.279
Male	0	234 (60%)	2778 (66%)	0.007
Race	0			0.079
White		270 (69%)	2648 (63%)
Black		47 (12%)	639 (15%)
Other		76 (19%)	900 (22%)
Etiology of liver disease	0			0.004
Viral		114 (29%)	1182 (28%)
Cryptogenic		34 (9%)	330 (8%)
Autoimmune		31 (8%)	197 (5%)
NASH		43 (11%)	454 (11%)
Alcoholic		89 (23%)	982 (23%)
HCC		28 (7%)	376 (9%)
AHN		16 (4%)	85 (2%)
Other		38 (10%)	581 (14%)
Diabetes	65	123 (32%)	1665 (40%)	0.001
Dialysis	0	109 (28%)	1963 (47%)	< 0.001
BMI (kg/m2)	5	29.0 (± 5.9)	28.3 (± 5.9)	0.044
Serum creatinine (mg/dL)	5	2.8 (± 2.1)	3.8 (± 2.6)	< 0.001
Bilirubin (mg/dL)	5	8.2 (± 11.7)	5.7 (± 9.2)	< 0.001
Albumin (mg/dL)	6	3.0 (± 0.8)	3.0 (± 0.7)	0.074
INR	5	1.9 (± 1.4)	1.6 (± 0.7)	< 0.001
MELD score	16	25.6 (± 10.5)	25.2 (± 8.7)	0.445
eGFR	5	37.5 (± 27.2)	26.8 (± 22.4)	< 0.001
Hepatic encephalopathy on wait list	31	308 (79%)	2882 (69%)	< 0.001
Liver allograft cold ischemia time	213	6.8 (± 2.6)	6.8 (± 3.5)	0.706
Yr of transplant	0	2009 (4)	2010 (4)	< 0.001

¹Covariates assessed at wait listing, apart from center volume over study period, hepatic encephalopathy on the wait list, liver allograft cold ischemic time, and year of transplant;

²P value by independent t-test for continuous variables and χ² test for categorical variables;

³Includes all liver transplants, not limited to LTA among patients listed for SLK. Descriptive characteristics by recipients of liver transplant alone or simultaneous liver-kidney transplant among patients listed for liver and kidney transplant in 2002-2015 (n = 4580). SD: Standard deviation; SLK: Simultaneous liver-kidney transplant; LTA: Liver transplant alone; BMI: Body mass index; INR: International normalized ratio; MELD: Model for end-stage liver disease; eGFR: Estimated glomerular filtration rate.

Table 2 Hazard model of survival after liver transplant alone or simultaneous liver-kidney transplant in patients listed for liver and kidney transplant

Variable1	HR	95%CI	P value
Transplant received
SLK	ref.
LTA	2.85	(2.21, 3.66)	< 0.001
Transplant center SLK volume2
Interaction with receiving LTA vs SLK	0.97	(0.95, 0.99)	0.010
Age (yr)	1.01	(1.01, 1.02)	< 0.001
Male	1.08	(0.94, 1.24)	0.285
Race
White	ref.
Black	1.17	(0.98, 1.39)	0.089
Other	0.79	(0.66, 0.94)	0.007
Etiology of liver disease
Viral	ref.
Cryptogenic	0.77	(0.61, 0.98)	0.033
Autoimmune	0.57	(0.41, 0.79)	0.001
NASH	0.79	(0.63, 1.01)	0.060
Alcoholic	0.65	(0.54, 0.77)	< 0.001
HCC	1.04	(0.83, 1.30)	0.721
AHN	1.10	(0.75, 1.63)	0.621
Other	0.77	(0.62, 0.97)	0.024
Diabetes	1.23	(1.08, 1.40)	0.002
Dialysis	1.41	(1.19, 1.67)	< 0.001
BMI (kg/m2)	0.98	(0.97, 0.99)	0.003
Serum creatinine (mg/dL)	0.97	(0.93, 1.01)	0.092
Bilirubin (mg/dL)	1.00	(0.98, 1.01)	0.394
Albumin (mg/dL)	0.88	(0.81, 0.96)	0.004
INR	0.92	(0.81, 1.05)	0.224
MELD score	1.00	(0.99, 1.02)	0.661
eGFR	1.00	(1.00, 1.01)	0.622
Hepatic encephalopathy on wait list	1.10	(0.94, 1.28)	0.221
Liver allograft cold ischemia time	1.00	(0.98, 1.02)	0.811
Year of transplant	0.98	(0.96, 1.00)	0.107

¹Covariates assessed at wait listing, apart from center volume over study period, hepatic encephalopathy on the wait list, liver allograft cold ischemic time, and year of transplant;

²Total number of SLK performed over study period (2/2002-12/2015), centered at 30 procedures, and divided by 10. Multivariable Cox proportional hazards model, with the baseline hazard stratified on the transplant center, of survival after liver transplant alone or simultaneous liver-kidney transplant among patients listed for liver and kidney transplant in 2002-2015 (n = 4257). HR: Hazard ratio; CI: Confidence interval; SLK: Simultaneous liver-kidney transplant; LTA: Liver transplant alone; NASH: Non-alcoholic steatohepatitis; HCC: Hepatocellular carcinoma; AHN: Acute hepatic necrosis; BMI: Body mass index; INR: International normalized ratio; MELD: Model for end-stage liver disease; eGFR: Estimated glomerular filtration rate.