A multi-factor analysis of kidney regraft outcomes

1. GENERAL: We updated prior analyses of renal retransplants reported to the UNOS Registry by estimating the compound effects of 22 covariates on regraft survival within 2 consecutive posttransplant risk periods. During an early risk period, 9,126 kidney-only regraft recipients were followed through one year, and, in a second risk period, 7,798 recipients whose regrafts survived beyond one year were followed for 5 years posttransplant. The study sample represented a unique set of patients whose first renal transplants were also recorded by the registry. 2. RELATIVE INFLUENCE OF TRANSPLANT FACTORS AND CENTER: From a multivariate log-linear analysis, the top 5 factors influencing one-year regraft survival rates were ranked as follows: 1) transplant center (accounted for 24% of the variation in short-term outcomes); 2) duration of first graft (19%); 3) donor age (15%); 4) recipient's body mass index (7%); and 5) year of transplant (6%). Ranking long-term outcomes demonstrated that donor age was the dominant factor governing the 5-year survival rates among regrafts, accounting for 30% of long-term variation. Transplant center, recipient age and race, and donor relationship accounted for another 16%, 14%, 10% and 8% of changes in long-term regraft survival, respectively. Despite center effects, a center's volume did not appear to be associated with outcome, and a center's short-term effect did not predict its long-term results, as the correlation between one- and 5-year center-specific rates was small (R = 0.11) and statistically insignificant (P = 0.15). 3. RECIPIENT FACTORS RELATED TO FIRST TRANSPLANT: Among 4 recipient factors related to a first transplant, only the first graft's survival duration significantly influenced both short- and long-term outcomes of regrafts. If the first graft survived for more than 2 years, a regraft had an approximate 90% chance of surviving to one year as compared with an 80% chance if the first graft failed within 2 years. Regrafts among recipients whose first graft lasted more than 4 3/4 years exhibited better 5-year survival rates (82.2%) versus the less-than-average rates for the other groups. 4. RECIPIENT FACTORS: Six of the 7 recipient factors selected for analysis significantly influenced short- or long-term regraft outcomes: 1) female recipients had significantly higher long-term regraft survival rates; 2) Black recipients of regrafts had poor long-term results; 3) children (0-12 yr) exhibited markedly diminished one-year regraft survival rates, and teenage recipients exhibited poor long-term regraft function; 4) obese recipients (body mass index > 30 kg/m2) had poor one-year and 5-year regraft survival rates; 5) impaired functional status immediately pre-retransplant significantly reduced both short- and long-term rates; and 6) regraft recipients whose PRA was above 0% exhibited diminished one-year and 5-year regraft survival rates. 5. DONOR FACTORS: Regraft recipients receiving a living donor's kidney had 87% one-year graft survival, outperforming cadaveric regrafts by 8 percentage points during the initial period. At 5 years, survival rates for patients receiving living related (except parents) or unrelated donor regrafts enjoyed above average 5-year survival rates, but parental and cadaver types of donors demonstrated poor long-term values. The strong short-term effect of donor age emanated from poorer regraft functions from both younger and older donors, whereas the long-term effect arose primarily as a result of the poor regraft functions from older donors. After 24 hours of cold ischemia time, early cadaveric regraft survival rates were significantly impaired. 6. TRANSPLANT FACTORS: This study clarified the effects of HLA mismatches and re-exposure to mismatched antigens on regraft survival rates. Generally, receiving a zero mismatched regraft was beneficial. Specifically, class I incompatible regrafts with repeat AB mismatches demonstrated superior long-term rates, even surpassing the 5-year results for 0 AB mismatches. Incompatible class II regrafts with re-exposure to DR antigens had marginal reductions in short- and long-term outcomes. Increasing numbers of HLA-AB mismatches did not seriously impact regraft survival, but any DR mismatch seriously reduced the one-year regraft survival rate.