PEDIATRIC DIALYSIS PATIENTS CONSIDERED TRANSPLANT CANDIDATES HAVE LESS MORTALITY RISK: A NAPRTCS REPORT

Abstract

476 North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) data suggest higher mortality rates in children treated with dialysis compared to transplantation. Patient selection may account for this disparity. Therefore, we evaluated mortality among transplant candidates on dialysis (TxC) compared to other maintenance dialysis patients characterized as not transplant candidates for medical reasons (NoTxC), in order to address this bias. To provide an unbiased assessment of transplantation effect, we then evaluated mortality among transplant recipients (TxR) compared to TxC. Analyses were based on NAPRTCS data for all 1,931 children (age < 21 yr) starting primary dialysis between 1/1/92 and 12/31/97. Biannual NAPRTCS data collection characterized transplant status as: (a) UNOS wait-listed, (b) transplant work-up in progress, or (c) not a transplant candidate. Time-dependent proportional Cox models were used, adjusting for age, sex, race and cause of ESRD. Dialysis Mortality: Overall, 5.9% (113/1,931) of children died on dialysis prior to transplantation; of these, 55 deaths occurred among NoTxC. A total of 1,459 patients (76%) were eventually considered TxC (593 wait-listed, 866 transplant work-up in progress). Use of a time-dependent variable to indicate NAPRTCS classification as TxC yielded an adjusted mortality relative risk (RR) of 0.53 (p < 0.01) comparing TxC to NoTxC, with the same time since ESRD onset. Comparing the subset of TxC who were wait-listed to NoTxC yielded a RR of death of 0.23 (p < 0.0001). Transplantation Effect: Among all 1,459 TxC, 883 were transplanted; 34 died on dialysis and 24 after transplantation. Using a time-dependent variable to indicate transplantation, the RR of death following transplantation was 0.80; 95% CI = (0.43, 1.49) compared to TxC. Among the 593 wait-listed patients, 373 were transplanted; 12 died on dialysis and 7 after transplantation. Within this subgroup, the adjusted RR of death following transplant was 0.40; 95% CI = (0.14, 1.33) compared to TxC patients at the same time since wait-listing. These results are consistent with reports in adults of significantly decreased mortality risk among dialysis patients considered TxC and emphasize the importance of selection bias in studies comparing mortality between dialysis and transplantation in children. These results also suggest a decreased mortality risk following transplantation among children medically eligible to be transplanted. However, these findings are limited by the relatively small number of deaths among pediatric transplantation candidates and recipients.