A kidney-paired donation (KPD) pool consists of transplant candidates and their incompatible donors, along with nondirected donors (NDDs). In a match run, exchanges are arranged among pairs in the pool via cycles, as well as chains created from NDDs. A problem of importance is how to arrange cycles and chains to optimize the number of transplants. We outline and examine, through example and by simulation, four schemes for selecting potential matches in a realistic model of a KPD system; proposed schemes take account of probabilities that chosen transplants may not be completed as well as allowing for contingency plans when the optimal solution fails. Using data on candidate/donor pairs and NDDs from the Alliance for Paired Donation, the simulations extend over 8 match runs, with 30 pairs and 1 NDD added between each run. Schemes that incorporate uncertainties and fallbacks into the selection process yield substantially more transplants on average, increasing the number of transplants by as much as 40% compared to a standard selection scheme. The gain depends on the degree of uncertainty in the system. The proposed approaches can be easily implemented and provide substantial advantages over current KPD matching algorithms.
In 2003, the US kidney allocation system was changed to eliminate priority for HLA-B similarity. We report outcomes from before and after this change using data from the Scientific Registry of Transplant Recipients (SRTR). Analyses were based on 108 701 solitary deceased donor kidney recipients during the 6 years before and after the policy change. Racial/ethnic distributions of recipients in the two periods were compared (chi-square); graft failures were analyzed using Cox models. In the 6 years before and after the policy change, the overall number of deceased donor transplants rose 23%, with a larger increase for minorities (40%) and a smaller increase for non-Hispanic whites (whites) (8%). The increase in the proportion of transplants for non-whites versus whites was highly significant (p < 0.0001). Two-year graft survival improved for all racial/ethnic groups after implementation of this new policy. Findings confirmed prior SRTR predictions. Following elimination of allocation priority for HLA-B similarity, the deficit in transplantation rates among minorities compared with that for whites was reduced but not eliminated; furthermore, there was no adverse effect on graft survival.
Coincident with an increasing national interest in equitable health care, a number of studies have described disparities in access to solid organ transplantation for minority patients. In contrast, relatively little is known about differences in posttransplant outcomes between patients of specific racial and ethnic populations. In this paper, we review trends in access to solid organ transplantation and posttransplant outcomes by organ type, race and ethnicity. In addition, we present an analysis of categories of factors that contribute to the racial/ethnic variation seen in kidney transplant outcomes. Disparities in minority access to transplantation among wait-listed candidates are improving, but persist for those awaiting kidney, simultaneous kidney and pancreas and intestine transplantation. In general, graft and patient survival among recipients of solid organ transplants is highest for Asians and Hispanic/Latinos, intermediate for whites and lowest for African Americans. Although much of the difference in outcomes between racial/ethnic groups can be accounted for by adjusting for patient characteristics, important observed differences remain Age and duration of pretransplant dialysis exposure emerge as the most important determinants of survival in an investigation of the relative impact of center-related versus patient-related variables on kidney graft outcomes.
Transplant tourism, where patients travel to foreign countries specifically to receive a transplant, is poorly characterized. This study examined national data to determine the minimum scope of this practice. US national waiting list removal data were analyzed. Waiting list removals for transplant without a corresponding US transplant in the database were reviewed via a data validation query to transplant centers to identify foreign transplants. Additionally, waiting list removal records with text field entries indicating a transplant abroad were identified. We identified 373 foreign transplants (173 directly noted; 200 from data validation); most (89.3%) were kidney transplants. Between 2001 and 2006, the annual number of waiting list removals for transplant abroad increased. Male sex, Asian race, resident and nonresident alien status and college education were significantly and independently associated with foreign transplant. Recipients from 34 states, plus the District of Columbia, received foreign transplants in 35 countries, led by China, the Philippines and India. Transplants in foreign countries among waitlisted candidates in the US are increasingly performed. The data reported here represent the minimum number of cases and the full extent of this practice cannot be determined using existing data. Additional reporting requirements are needed.
Growth in the number of active patients on the kidney transplant waiting list has slowed. Projections based on the most recent 5-year data suggest the total waiting list will grow at a rate of 4138 registrations per year, whereas the active waiting list will increase at less than one-sixth that rate, or 663 registrations per year. The last 5 years have seen a small trend toward improved unadjusted allograft survival for living and deceased donor kidneys. Since 2004 the overall number of pancreas transplants has declined. Among pancreas recipients, those with simultaneous kidney-pancreas transplants experienced the highest pancreas graft survival rates.In response to the ongoing shortage of deceased donor organs, the US Health Resources and Services Administration launched the Organ Donation Breakthrough Collaborative in September 2003 and the Organ Transplantation Breakthrough Collaborative (OTBC) in October 2005. The 58 DSA Challenge is prominent among the goals adopted by the OTBC. Its premise: were each of the 58 existing donation service areas to increase the number of kidney transplants performed within their boundaries by 10 per month, an additional 7000 transplants over current annual levels would result. Such an increase could potentially eliminate the national kidney transplantation waiting list by 2030.
This article focuses on geographic variability in patient access to kidney transplantation in the United States. It examines geographic differences and trends in access rates to kidney transplantation, in the component rates of wait-listing, and of living and deceased donor transplantation. Using data from Centers for Medicare and Medicaid Services and the Organ Procurement and Transplantation Network/Scientific Registry of Transplant Recipients, we studied 700,000+ patients under 75, who began chronic dialysis treatment, received their first living donor kidney transplant, or were placed on the waiting list pre-emptively. Relative rates of wait-listing and transplantation by State were calculated using Cox regression models, adjusted for patient demographics. There were geographic differences in access to the kidney waiting list and to a kidney transplant. Adjusted wait-list rates ranged from 37% lower to 64% higher than the national average. The living donor rate ranged from 57% lower to 166% higher, while the deceased donor transplant rate ranged from 60% lower to 150% higher than the national average. In general, States with higher wait-listing rates tended to have lower transplantation rates and States with lower wait-listing rates had higher transplant rates. Six States demonstrated both high wait-listing and deceased donor transplantation rates while six others, plus D.C. and Puerto Rico, were below the national average for both parameters.
Understanding how transplant data are collected is crucial to understanding how the data can be used. The collection and use of Organ Procurement and Transplantation Network/Scientific Registry of Transplant Recipients (OPTN/SRTR) data continues to evolve, leading to improvements in data quality, timeliness and scope while reducing the data collection burden. Additional ascertainment of outcomes completes and validates existing data, although caveats remain for researchers. We also consider analytical issues related to cohort choice, timing of data submission, and transplant center variations in follow-up data. All of these points should be carefully considered when choosing cohorts and data sources for analysis. The second part of the article describes some of the statistical methods for outcome analysis employed by the SRTR. Issues of cohort and follow-up period selection lead into a discussion of outcome definitions, event ascertainment, censoring and covariate adjustment. We describe methods for computing unadjusted mortality rates and survival probabilities, and estimating covariate effects through regression modeling. The article concludes with a description of simulated allocation modeling, developed by the SRTR for comparing outcomes of proposed changes to national organ allocation policies.
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CONTEXT:Transplantation using kidneys from deceased donors who meet the expanded criteria donor (ECD) definition (age > or =60 years or 50 to 59 years with at least 2 of the following: history of hypertension, serum creatinine level >1.5 mg/dL [132.6 micromol/L], and cerebrovascular cause of death) is associated with 70% higher risk of graft failure compared with non-ECD transplants. However, if ECD transplants offer improved overall patient survival, inferior graft outcome may represent an acceptable trade-off. OBJECTIVE:To compare mortality after ECD kidney transplantation vs that in a combined standard-therapy group of non-ECD recipients and those still receiving dialysis. DESIGN, SETTING, AND PATIENTS:Retrospective cohort study using data from a US national registry of mortality and graft outcomes among kidney transplant candidates and recipients. The cohort included 109,127 patients receiving dialysis and added to the kidney waiting list between January 1, 1995, and December 31, 2002, and followed up through July 31, 2004. MAIN OUTCOME MEASURE:Long-term (3-year) relative risk of mortality for ECD kidney recipients vs those receiving standard therapy, estimated using time-dependent Cox regression models. RESULTS:By end of follow-up, 7790 ECD kidney transplants were performed. Because of excess ECD recipient mortality in the perioperative period, cumulative survival did not equal that of standard-therapy patients until 3.5 years posttransplantation. Long-term relative mortality risk was 17% lower for ECD recipients (relative risk, 0.83; 95% confidence interval, 0.77-0.90; P<.001). Subgroups with significant ECD survival benefit included patients older than 40 years, both sexes, non-Hispanics, all races, unsensitized patients, and those with diabetes or hypertension. In organ procurement organizations (OPOs) with long median waiting times (>1350 days), ECD recipients had a 27% lower risk of death (relative risk, 0.73; 95% confidence interval, 0.64-0.83; P<.001). In areas with shorter waiting times, only recipients with diabetes demonstrated an ECD survival benefit. CONCLUSIONS:ECD kidney transplants should be offered principally to candidates older than 40 years in OPOs with long waiting times. In OPOs with shorter waiting times, in which non-ECD kidney transplant availability is higher, candidates should be counseled that ECD survival benefit is observed only for patients with diabetes.
BACKGROUND Benefits in terms of reductions in mortality corresponding to improvements in Kidney Disease Outcomes Quality Initiative (K/DOQI) compliance for adequacy of dialysis dose and anemia control have not been documented in the literature. We studied changes in achieving K/DOQI guidelines at the facility level to determine whether those changes are associated with corresponding changes in mortality. METHODS Adjusted mortality and fractions of patients achieving K/DOQI guidelines for urea reduction ratios (URRs; > or =65%) and hematocrit levels (> or =33%) were computed for 2,858 dialysis facilities from 1999 to 2002 using national data for patients with end-stage renal disease. Linear and Poisson regression were used to study the relationship between K/DOQI compliance and mortality and between changes in compliance and changes in mortality. RESULTS In 2002, facilities in the lowest quintile of K/DOQI compliance for URR and hematocrit guidelines had 22% and 14% greater mortality rates (P < 0.0001) than facilities in the highest quintile, respectively. A 10-percentage point increase in fraction of patients with a URR of 65% or greater was associated with a 2.2% decrease in mortality (P = 0.0006), and a 10-percentage point increase in percentage of patients with a hematocrit of 33% or greater was associated with a 1.5% decrease in mortality (P = 0.003). Facilities in the highest tertiles of improvement for URR and hematocrit had a change in mortality rates that was 15% better than those observed for facilities in the lowest tertiles (P < 0.0001). CONCLUSION Both current practice and changes in practices with regard to achieving anemia and dialysis-dose guidelines are associated significantly with mortality outcomes at the dialysis-facility level.
It is highly desirable to base decisions designed to improve medical practice or organ allocation policies on the analyses of the most recent data available. Yet there is often a need to balance this desire with the added value of evaluating long-term outcomes (e.g. 5-year mortality rates), which requires the use of data from earlier years. This article explains the methods used by the Scientific Registry of Transplant Recipients in order to achieve these goals simultaneously.The analysis of waiting list and transplant outcomes depends strongly on statistical methods that can combine data from different cohorts of patients that have been followed for different lengths of time. A variety of statistical methods have been designed to address these goals, including the Kaplan-Meier estimator, Cox regression models, and Poisson regression.An in-depth description of the statistical methods used for calculating waiting times associated with the various types of organ transplants is provided. Risk of mortality and graft failure, adjusted analyses, cohort selection, and the many complicating factors surrounding the calculation of follow-up time for various outcomes analyses are also examined.
Data from the Scientific Registry of Transplant Recipients offer a unique and comprehensive view of US trends in kidney and pancreas waiting list characteristics and outcomes, transplant recipient and donor characteristics, and patient and allograft survival. Important findings from our review of developments during 2002 and the decade's transplantation trends appear below.The kidney waiting list has continued to grow, increasing from 47 830 in 2001 to 50 855 in 2002. This growth has occurred despite the increasing importance of living donor transplantation, which rose from 28% of total kidney transplants in 1993 to 43% in 2002.Policies and procedures to expedite the allocation of expanded criteria donor (ECD) kidneys were developed and implemented during 2002, when 15% of deceased donor transplants were performed with ECD kidneys. Unadjusted 1- and 5-year deceased donor kidney allograft survivals were 81% and 51% for ECD kidney recipients, and 90% and 68% for non-ECD kidney recipients, respectively.Although more patients have been placed on the simultaneous kidney-pancreas waiting list, the number of these transplants dropped from a peak of 970 in 1998 to 905 in 2002. This decline may be due to competition for organs from increasing numbers of isolated pancreas and islet transplants.