Predictors of graft function and survival in second kidney transplantation: A single center experience

Table 1 Characteristics of recipients, donors, first kidney transplantation, and second kidney transplantation, n (%)

Variable		Value1
Recipient age at SKT (yr)		47.5 (41.3-56; 24-70)
Recipient sex	Male	33 (68.8)
	Female	15 (31.3)
Recipient BMI (kg/m2) at SKT		24.7 (22.13-26.95; 19-33.5)
Causes of ESRD	Glomerulonephritis	16 (33.3)
	DM	1 (2.1)
	Hypertension	4 (8.3)
	PCKD	4 (8.3)
	Others	23 (47.9)
Overall duration of dialysis (mo.)		95 (76-121.8; 29-244)
Start of first graft function	PNF	23 (47.9)
	DGF	8 (16.7)
	Immediate	17 (35.4)
GFR one year after FKT (mL/min/1.73 m2)		0 (0-29.3; 0-78.8)
Attacks of acute rejection in first year after FKT2		0 (0-1; 0-6)
First graft loss due to rejection		3 (6.3)
First graft nephrectomy		37 (77.1)
SKT donor type	Living	3 (6.3)
	Deceased	45 (93.8)
SKT donor age (yr)		50 (36.3-60.8; 16-74)
Recipient age minus donor age (yr) at SKT		0 (-10-7; -39-34)
SKT donor BMI (kg/m2)		25 (23-27; 19-37.9)
Recipient BMI minus donor BMI (kg/m2) at SKT		-0.45 (-3.8-3.15; -16.7-9.6)
SKT PRA level	0-30%	35 (72.9)
	31-80%	10 (20.8)
	> 80%	3 (6.3)
SKT HLA mismatches		2 (1.3-3.8; 0-6)
SKT laterality relative to FKT	Ipsilateral	1 (2.1)
	Contralateral	47 (97.9)
Number of renal arteries at SKT	Single	43 (89.6)
	Double	5 (10.4)
SKT operative time (min)		140 (113-170; 82-236)
SKT ischemia time (min)		708 (531-897; 74-1319)
SKT operative revision		24 (50)
SKT vascular complications		8 (16.7)
Start of second graft function	PNF	5 (10.4)
	DGF	10 (20.8)
	Immediate	33 (68.8)
Attacks of acute rejection in first year after SKT		0 (0-1; 0-3)
GFR one year after SKT (mL/min/1.73 m2)		36 (22.8-52.8; 0-82.4)

¹Quantitative variables are expressed as median (IQR; range), while categorical variables are expressed as count (percentage).

²Two missing cases.

BMI: Body mass index; DM: Diabetes mellitus; DGF: Delayed graft function; ESRD: End-stage renal disease; FKT: First kidney transplantation; GFR: Glomerular filtration rate; HLA: Human leucocytic antigen; PCKD: Polycystic kidney disease; PNF: Primary non-function; PRA: Panel reactive antibodies; SKT: Second kidney transplantation.

Table 2 Survival probabilities of the graft and the patient after the second kidney transplantation by Kaplan-Meier analyses

Follow-up time (months)	Second graft survival			Patient survival after second kidney transplantation
	Survival probability (%)	Upper 95% confidence limit	Lower 95% confidence limit	Survival probability (%)	Upper 95% confidence limit	Lower 95% confidence limit
12	90.53	+5.81	-13.84	97.87	+1.83	-12.04
36	79.88	+9.55	-16.22	95.60	+3.29	-12.10
60	73.71	+11.31	-17.34	91.92	+5.51	-15.82
120	51.57	+21.01	-26.12	83.04	+9.90	-20.65
174 (study max.)	51.57	+21.01	-26.12	83.04	+9.90	-20.65

Table 3 Quantitative predictors (normally distributed over both outcome groups) of primary non-function second graft by the independent-samples t test

	Primary non-function (n = 5)		Primary function (n = 43)		P value1
	Mean	SE	Mean	SE
Recipient age (yr)	47.8	5.4	47.9	1.8	0.98
Donor age (yr)	49.6	7.5	48.0	2.2	0.82
Recipient BMI (kg/m2)	28.04	0.83	24.20	0.47	0.009
Total ischemia time (min)	655	98	711	48	0.70
Operative time (min)	150	20	142	6	0.66

¹Since Levene’s test yielded no significant differences between variances of outcome groups for the five tested predictors, equal variances were assumed. BMI: Body mass index.

Table 4 Quantitative predictors (non-normally distributed over one or both outcome groups) of primary non-function second graft by the independent-samples Mann-Whitney U test

	Primary non-function (n = 5)		Primary function (n = 43)		P value
	Median	Mean rank	Median	Mean rank
Duration of first graft function (mo)	0	17.6	4	25.3	0.26
Total duration of dialysis before second transplantation (including before first transplantation) (mo)	93	19.3	96	25.1	0.39

Table 5 Categorical predictors of primary non-function second graft by Fisher’s exact test

Variables		Primary non-function (n = 5)	Primary function (n = 43)1	Odds ratio2	P value
DM as a cause of ESRD	No	5	42	0	1
	Yes	0	1
First graft function	No	3	20		0.84
	Delayed	1	7
	Instant	1	16
Acute rejection in first year after first transplantation	No	3	24	0.94	1
	Yes	2	17
First graft loss by acute rejection	No	3	42	28	0.025
	Yes	2	1
First graft nephrectomy	No	0	11	Not assessed3	0.58
	Yes	5	32
Living donor	No	5	40	0	1
	Yes	0	3
PRA grouping	0% to 30%	3	32		0.33
	31% to 80%	1	9
	Over 80%	1	2
Number of HLA mismatches	0	1	6		0.51
	1 to 3	2	27
	4 to 6	2	10
Over one artery	No	5	38	0	1
	Yes	0	5
Vascular complications	No	3	37	4.1	0.19
	Yes	2	6

¹Except for acute rejection in first year after first transplantation, where n = 41 because two cases are missing.

²Odds of primary non-function in the presence of the predictor to odds of primary non-function in its absence.

³Not assessed, for the calculation entails division by zero.

DM: Diabetes mellitus; ESRD: End-stage renal disease; HLA: Human leukocytic antigens; PRA: Panel reactive antibodies.

Table 6 Categorical predictors of second graft survival by the log-rank test for Kaplan-Meier curves

Variables		Events (n = 13)	Censored (n = 30)1	Log-rank statistic	P value
DM as a cause of ESRD	No	12	30	1.218	0.270
	Yes	1	0
First graft function	No	2	18	9.684	0.008
	Delayed	4	3
	Instant	7	9
Acute rejection in first year after first transplantation	No	5	19	3.757	0.053
	Yes	8	9
First graft loss by acute rejection	No	13	29	0.369	0.543
	Yes	0	1
First graft nephrectomy	No	3	8	0.097	0.756
	Yes	10	22
Living donor	No	12	28	0.002	0.965
	Yes	1	2
PRA grouping	0% to 30%	11	21	0.693	0.707
	31% to 80%	2	7
	Over 80%	0	2
Number of HLA mismatches	0	2	4	0.106	0.948
	1 to 3	8	19
	4 to 6	3	7
Over one artery	No	10	28	1.584	0.208
	Yes	3	2
Vascular complications	No	13	24	1.723	0.189
	Yes	0	6
Delayed second graft function	No	7	26	12.238	0.0005
	Yes	6	4

¹Except for acute rejection in first year after first transplantation, where n = 28 because two cases are missing.

BMI: Body mass index; DM: Diabetes mellitus; ESRD: End-stage renal disease; HLA: Human leukocytic antigens; PRA: Panel reactive antibodies.

Table 7 Quantitative predictors of second graft survival by Cox regression

Variables	HR	95%CI for HR		P value	P value for PH testing1
		Lower bound	Upper bound
Recipient age (yr)	0.976	0.930	1.023	0.306	0.074
Recipient BMI (kg/m2)	0.980	0.810	1.185	0.833	0.787
Duration of first graft function (mo)	1.007	0.994	1.020	0.307	0.059
Total duration of dialysis before second transplantation (including before first transplantation) (mo)	1.006	0.995	1.017	0.295	0.061
Donor age (yr)	1.016	0.979	1.055	0.396	0.852
Recipient age minus donor age (yr)	0.972	0.937	1.009	0.140	0.306
Recipient BMI minus donor BMI (kg/m2)	0.984	0.893	1.085	0.751	0.410
Total ischemia time (min)	1.001	0.999	1.003	0.284	0.579
Operative time (min)	0.995	0.979	1.010	0.497	0.363

¹Testing of the proportional hazards assumption was done by correlating ranked survival times with Schoenfeld residuals.

BMI: Body mass index; HR: Hazard ratio; PH: Proportional hazards.