Pediatr Transplantation 2014: 18: 689–697
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Pediatric Transplantation DOI: 10.1111/petr.12322
Racial disparities in pediatric kidney transplantation in New Zealand Grace BS, Kara T, Kennedy SE, McDonald SP. (2014) Racial disparities in pediatric kidney transplantation in New Zealand. Pediatr Transplant, 18: 689–697. DOI: 10.1111/petr.12322 Abstract: Racial disparities in transplantation rates and outcomes have not been investigated in detail for NZ, a country with unique demographics. We studied a retrospective cohort of 215 patients 50%), and number of HLA mismatches were also investigated. Date of first acceptance onto the deceased donor kidney waiting list was extracted from hospital records for patients who commenced RRT after 2003. Patients who received live donor pre-emptive transplants were excluded. Waiting list data were not available for patients transplanted via Wellington Hospital.
Variables Race was defined as either Maori, Pacific people, Asian, and European. Patient age at commencement of RRT was categorized into three groups (0–2, 3–10, and 11–17 yr)
690
based on likely transplantation and correlations with primary kidney disease, similar to previous work (10). Primary kidney diseases were grouped into five categories: glomerulonephritis (excluding familial glomerulonephritis and Alport’s syndrome), urological (reflux nephropathy, posterior urethral valves, and other urological disorders), genetic and familial diseases (including all polycystic diseases, medullary cystic disease, Alport’s syndrome, cystinosis and oxalosis), renal hypoplasia/dysplasia, and all other diseases. Late referral was defined as referral to nephrological care within three months of commencing RRT. This was only defined for patients older than three months at commencement and only recorded for patients commencing RRT after March 1997. Patients were considered sensitized if PRA pretransplant were ≥50%, donor age was categorized as 0–24, 25–49, and ≥60 yr, time on dialysis pretransplant was categorized 0 (pre-emptive), 0.1–23.9, and ≥24 months, total ischemic time 1–1.9, 2–11.9, and ≥12 h. Delayed graft function was defined as the need for dialysis within 72 h of transplant and was only recorded after March 1994.
Analysis Categorical variables were compared using Fisher’s exact test and continuous variables using Kruskal–Wallis test and stratified by donor source where appropriate. Time to event analyses used Kaplan–Meier estimates of survival or failure after five yr. Patient survival was analyzed using Cox models. Uptake of transplantation after starting RRT, first rejection after transplant, and graft survival were analyzed using Cox proportional hazard models, with patients censored at 31 December 2012 or death. Patient survival and time to first placement onto the waiting list from commencement of RRT were analyzed similarly. Unless stated otherwise, analyses of uptake of transplantation were adjusted for primary kidney disease, gender, and patient age and era (1990–1999 vs. 2000–2012) at commencement. Results are presented as HR, with 95% confidence intervals. Analyses of graft and patient survival were adjusted for age at transplant, sensitization, HLA mismatches, primary kidney disease, transplantation era, donor age, time on dialysis, ischemic time, and transplanting hospital, with the underlying hazard function stratified by donor source (live or deceased donor). Additional analyses of time to first transplant were completed, with interaction terms for race by era.
Results Patients
Since 1990, 218 patients started RRT while younger than 18 yr in NZ, but one patient was excluded because she received her first transplant overseas and two were excluded because they received other organs (one heart and one liver). Pacific patients comprised 11 Cook Islanders, 13 Samoan, four Tongans, one Tokelauan, and one Tuvaluan. Asian patients comprised three Chinese, six Indian, and one each of Filipino, Vietnamese, and Japanese heritage. All Maori and all but four European patients were born in NZ,
Kidney transplantation in New Zealand
whereas most Asian patients were born elsewhere (Table 1). There were considerably more patients after 2000 than before in all age groups, possibly with the exception of Pacific patients. Glomerulonephritis, including FSGS, was more common in non-Europeans, especially Pacific patients. Of the 30 Pacific patients, seven had FSGS (23.3%), compared with 11 European patients (8.8%). As a result, proportionally more Europeans had genetic/familial, urologic or hypoplastic/dysplastic diseases (Table 1). Patient age at commencement was not associated with race. Patient mortality
There were 35 deaths (15 European, 15 Maori, and five Pacific) in 2107 patient-years of followup. M aori patients had the highest mortality rates on RRT (Table 2, Fig. 1). Survival did not vary significantly over time (HR 2000–2012 vs. 1990–1999 1.09, 95% CI 0.45–2.64). Time to first transplant
receive a transplant (Fig. 2, median time on dialysis 8.2 months, 95% CI 6.3–12.8, this could not be reliably estimated for other races using Kaplan–Meier methods). Maori and Pacific patients were considerably less likely to receive a live donor graft (Fig. 2) and did not receive any preemptive transplants (Table 3). Maori and Pacific patients were more likely to receive a deceased donor kidney than Europeans (Fig. 2). We detected no overall change in uptake of transplantation over time (HR after 1999 vs. before 1999; 1.07, 95% CI 0.69–1.65). However, race by era interactions were apparent. Compared with 1990–1999, Maori were possibly less likely to receive a transplant 2000–2012 (HR 0.42, 95% CI 0.18–1.00, p = 0.050 for era: M aori interaction), as were Asian (HR 0.2, 95% CI 0.06–0.71, p = 0.012 for era: Asian interaction), and Pacific patients were possibly less likely (HR 0.50, 95% CI 0.20–1.27, p = 0.15 for era: Pacific interaction). Of the seven Pacific patients with FSGS, four were transplanted. Placement onto the waiting list
Most patients (161% or 74.5%) received at least one kidney graft by 31 December 2012, and 31 (14.3%) patients received a pre-emptive transplant. European patients were the most likely to
Of the 89 patients who commenced RRT 2003– 2012, waiting list status was available for 63 patients, and 54 of whom were listed. Within two yr of starting RRT, 81% (95% CI 70–90) of
Table 1. Pediatric patients who commenced renal replacement therapy in NZ 1990–2012, by racial group Factor N Age at commencement (yr) 0–2 3–10 11–17 Born in NZ Male Primary kidney disease Glomerulonephritis Genetic/familial Urological Other Era 1990–1999 2000–2012 Late referral* Not referred late Referred late First transplant Live donor Deceased donor Dead without transplant Dialyzing as of 31 December 2012 Transplanted within 5 yr, % (95% CI) 5-yr patient survival, % (95% CI)
Maori
Pacific
125
48
30
25 (20.0%) 35 (28.0%) 65 (52.0%) 121 (96.8%) 63 (50.4%)
5 (10.4%) 13 (27.1%) 30 (62.5%) 48 (100.0%) 22 (45.8%)
1 (3.3%) 10 (33.3%) 19 (63.3%) 22 (73.3%) 13 (43.3%)
0 (0.0%) 3 (25.0%) 9 (75.0%) 6 (50.0%) 4 (33.3%)
36 (28.8%) 29 (23.2%) 38 (30.4%) 22 (17.6%)
24 (50.0%) 5 (10.4%) 8 (16.7%) 11 (22.9%)
23 (76.7%) 2 (6.7%) 3 (10.0%) 2 (6.7%)
7 (58.3%) 0 (0.0%) 1 (8.3%) 4 (33.3%)
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Pediatric Transplantation DOI: 10.1111/petr.12322
Racial disparities in pediatric kidney transplantation in New Zealand Grace BS, Kara T, Kennedy SE, McDonald SP. (2014) Racial disparities in pediatric kidney transplantation in New Zealand. Pediatr Transplant, 18: 689–697. DOI: 10.1111/petr.12322 Abstract: Racial disparities in transplantation rates and outcomes have not been investigated in detail for NZ, a country with unique demographics. We studied a retrospective cohort of 215 patients 50%), and number of HLA mismatches were also investigated. Date of first acceptance onto the deceased donor kidney waiting list was extracted from hospital records for patients who commenced RRT after 2003. Patients who received live donor pre-emptive transplants were excluded. Waiting list data were not available for patients transplanted via Wellington Hospital.
Variables Race was defined as either Maori, Pacific people, Asian, and European. Patient age at commencement of RRT was categorized into three groups (0–2, 3–10, and 11–17 yr)
690
based on likely transplantation and correlations with primary kidney disease, similar to previous work (10). Primary kidney diseases were grouped into five categories: glomerulonephritis (excluding familial glomerulonephritis and Alport’s syndrome), urological (reflux nephropathy, posterior urethral valves, and other urological disorders), genetic and familial diseases (including all polycystic diseases, medullary cystic disease, Alport’s syndrome, cystinosis and oxalosis), renal hypoplasia/dysplasia, and all other diseases. Late referral was defined as referral to nephrological care within three months of commencing RRT. This was only defined for patients older than three months at commencement and only recorded for patients commencing RRT after March 1997. Patients were considered sensitized if PRA pretransplant were ≥50%, donor age was categorized as 0–24, 25–49, and ≥60 yr, time on dialysis pretransplant was categorized 0 (pre-emptive), 0.1–23.9, and ≥24 months, total ischemic time 1–1.9, 2–11.9, and ≥12 h. Delayed graft function was defined as the need for dialysis within 72 h of transplant and was only recorded after March 1994.
Analysis Categorical variables were compared using Fisher’s exact test and continuous variables using Kruskal–Wallis test and stratified by donor source where appropriate. Time to event analyses used Kaplan–Meier estimates of survival or failure after five yr. Patient survival was analyzed using Cox models. Uptake of transplantation after starting RRT, first rejection after transplant, and graft survival were analyzed using Cox proportional hazard models, with patients censored at 31 December 2012 or death. Patient survival and time to first placement onto the waiting list from commencement of RRT were analyzed similarly. Unless stated otherwise, analyses of uptake of transplantation were adjusted for primary kidney disease, gender, and patient age and era (1990–1999 vs. 2000–2012) at commencement. Results are presented as HR, with 95% confidence intervals. Analyses of graft and patient survival were adjusted for age at transplant, sensitization, HLA mismatches, primary kidney disease, transplantation era, donor age, time on dialysis, ischemic time, and transplanting hospital, with the underlying hazard function stratified by donor source (live or deceased donor). Additional analyses of time to first transplant were completed, with interaction terms for race by era.
Results Patients
Since 1990, 218 patients started RRT while younger than 18 yr in NZ, but one patient was excluded because she received her first transplant overseas and two were excluded because they received other organs (one heart and one liver). Pacific patients comprised 11 Cook Islanders, 13 Samoan, four Tongans, one Tokelauan, and one Tuvaluan. Asian patients comprised three Chinese, six Indian, and one each of Filipino, Vietnamese, and Japanese heritage. All Maori and all but four European patients were born in NZ,
Kidney transplantation in New Zealand
whereas most Asian patients were born elsewhere (Table 1). There were considerably more patients after 2000 than before in all age groups, possibly with the exception of Pacific patients. Glomerulonephritis, including FSGS, was more common in non-Europeans, especially Pacific patients. Of the 30 Pacific patients, seven had FSGS (23.3%), compared with 11 European patients (8.8%). As a result, proportionally more Europeans had genetic/familial, urologic or hypoplastic/dysplastic diseases (Table 1). Patient age at commencement was not associated with race. Patient mortality
There were 35 deaths (15 European, 15 Maori, and five Pacific) in 2107 patient-years of followup. M aori patients had the highest mortality rates on RRT (Table 2, Fig. 1). Survival did not vary significantly over time (HR 2000–2012 vs. 1990–1999 1.09, 95% CI 0.45–2.64). Time to first transplant
receive a transplant (Fig. 2, median time on dialysis 8.2 months, 95% CI 6.3–12.8, this could not be reliably estimated for other races using Kaplan–Meier methods). Maori and Pacific patients were considerably less likely to receive a live donor graft (Fig. 2) and did not receive any preemptive transplants (Table 3). Maori and Pacific patients were more likely to receive a deceased donor kidney than Europeans (Fig. 2). We detected no overall change in uptake of transplantation over time (HR after 1999 vs. before 1999; 1.07, 95% CI 0.69–1.65). However, race by era interactions were apparent. Compared with 1990–1999, Maori were possibly less likely to receive a transplant 2000–2012 (HR 0.42, 95% CI 0.18–1.00, p = 0.050 for era: M aori interaction), as were Asian (HR 0.2, 95% CI 0.06–0.71, p = 0.012 for era: Asian interaction), and Pacific patients were possibly less likely (HR 0.50, 95% CI 0.20–1.27, p = 0.15 for era: Pacific interaction). Of the seven Pacific patients with FSGS, four were transplanted. Placement onto the waiting list
Most patients (161% or 74.5%) received at least one kidney graft by 31 December 2012, and 31 (14.3%) patients received a pre-emptive transplant. European patients were the most likely to
Of the 89 patients who commenced RRT 2003– 2012, waiting list status was available for 63 patients, and 54 of whom were listed. Within two yr of starting RRT, 81% (95% CI 70–90) of
Table 1. Pediatric patients who commenced renal replacement therapy in NZ 1990–2012, by racial group Factor N Age at commencement (yr) 0–2 3–10 11–17 Born in NZ Male Primary kidney disease Glomerulonephritis Genetic/familial Urological Other Era 1990–1999 2000–2012 Late referral* Not referred late Referred late First transplant Live donor Deceased donor Dead without transplant Dialyzing as of 31 December 2012 Transplanted within 5 yr, % (95% CI) 5-yr patient survival, % (95% CI)
Maori
Pacific
125
48
30
25 (20.0%) 35 (28.0%) 65 (52.0%) 121 (96.8%) 63 (50.4%)
5 (10.4%) 13 (27.1%) 30 (62.5%) 48 (100.0%) 22 (45.8%)
1 (3.3%) 10 (33.3%) 19 (63.3%) 22 (73.3%) 13 (43.3%)
0 (0.0%) 3 (25.0%) 9 (75.0%) 6 (50.0%) 4 (33.3%)
36 (28.8%) 29 (23.2%) 38 (30.4%) 22 (17.6%)
24 (50.0%) 5 (10.4%) 8 (16.7%) 11 (22.9%)
23 (76.7%) 2 (6.7%) 3 (10.0%) 2 (6.7%)
7 (58.3%) 0 (0.0%) 1 (8.3%) 4 (33.3%)
