Education is associated with reduction in racial disparities in kidney transplant outcome.

In this study, we hypothesized that higher level of education might be associated with reduced racial disparities in renal transplantation outcomes. We used data from the United States Renal Data System (September 1, 1990-September 1, 2007) (n=79,223) and analyzed two outcomes, graft loss and recipient mortality, using Cox models. Compared with whites, African Americans had increased risk of graft failure (HR, 1.48; p<0.001) and recipient mortality (HR, 1.06; p=0.004). Compared with recipients who graduated from college, all other education groups had inferior graft survival. Specifically, compared with college-graduated individuals, African Americans who never finished high school had the highest risk of graft failure (HR, 1.45; p<0.001), followed by high school graduates (HR, 1.27; p<0.001) and those with some college education (HR, 1.18; p<0.001). A similar trend was observed in whites. In African Americans (compared with whites), the highest risk of graft failure was associated with individuals who did not complete high school (HR, 1.96; p<0.001) followed by high school graduates (HR, 1.47; p<0.001), individuals with some college education (HR, 1.45; p<0.001), and college graduates (HR, 1.39; p<0.001). A similar trend was observed with recipient mortality. In sum, higher education was associated with reduced racial disparities in graft and recipient survival.

Effect of education on racial disparities in access to kidney transplantation.

Higher education level might result in reduced disparities in access to renal transplantation. We analyzed two outcomes: (i) being placed on the waiting list or transplanted without listing and (ii) transplantation in patients who were placed on the waiting list. We identified 3224 adult patients with end-stage renal disease (ESRD) in United States Renal Data System with education information available (mean age of ESRD onset of 57.1 ± 16.2 yr old, 54.3% men, 64.2% white, and 50.4% diabetics). Compared to whites, fewer African Americans graduated from college (10% vs. 16.7%) and a higher percentage never graduated from the high school (38.6% vs. 30.8%). African American race was associated with reduced access to transplantation (hazard ratio [HR] 0.70, p < 0.001 for wait-listing/transplantation without listing; HR 0.58, p < 0.001 for transplantation after listing). African American patients were less likely to be wait-listed/transplanted in the three less-educated groups: HR 0.67 (p = 0.005) for those never completed high school, HR 0.76 (p = 0.02) for high school graduates, and HR 0.65 (p = 0.003) for those with partial college education. However, the difference lost statistical significance in those who completed college education (HR 0.75, p = 0.1). In conclusion, in comparing white and African American candidates, racial disparities in access to kidney transplantation do exist. However, they might be alleviated in highly educated individuals.

The role of the economic environment in kidney transplant outcomes.

The relationship between global economic indicators and kidney allograft and patient survival is unknown. To investigate possible relationships between the two, we analyzed kidney transplant recipients receiving transplants between January of 1995 and December of 2002 (n = 105,181) in the USA using Cox regression models. We found that: The Dow Jones Industrial Average had a negative association with outcome at one year post-transplant (HR 1.03 and 1.06, p < 0.001 for graft and recipient survival, respectively) but changed to a protective effect in the late period (HR 0.77, p < 0.001, and HR 0.83, p < 0.001 for graft and recipient survival, respectively, five yr after transplantation). Unemployment rate had a protective effect at the time of transplantation (HR 0.97, p < 0.005) and at one year after transplantation (HR 0.95, p < 0.005) but changed to the opposite in the late period at the fifth post-transplant year (HR 1.35, p < 0.001, and HR 1.20, p < 0.001, for graft and recipient survival respectively). The Consumer Price Index measured at different post-transplant time points seems to have had a protective effect on the graft (HR 0.77, p < 0.001 at five yr) and recipient (HR 0.83, p < 0.001 at five yr) survival. Beyond three yr after transplantation, when some of the recipients lose Medicare benefits, economic downturns might have a negative association with the kidney graft and recipient survival.

The impact of employment status on recipient and renal allograft survival.

BACKGROUND: With the improved median survival of kidney transplant recipients, there has been an increased focus on quality of life after transplantation. Employment is a widely recognized component of quality of life. To date, no study has demonstrated a link between post-transplant employment status and recipient and allograft survival after transplant. METHODS: The records from the United States Renal Data System (USRDS) and the United Network for Organ Sharing (UNOS) from January 1, 1995, through December 31, 2002, were examined in this retrospective study. Two outcomes, allograft survival time (time between the transplantation and allograft failure or censor) and recipient survival time (time between the transplantation and recipient death or censor), were analyzed using Cox models adjusted for potential confounding factors. RESULTS: Compared to patients working full time at the time of transplantation, those not working by choice have a greater risk to graft [hazard ratio (HR) 1.27, p < 0.001] but not to recipient survival. A similar trend was observed in patients not working at 12 months post-transplant (HR 1.30, p < 0.001 for graft survival but not for recipient survival). However, at five-yr post-transplant not working by choice was protective to the graft (HR 0.47, p < 0.01) as compared to working full time. Results of the analysis in the patient subgroups based on the comorbidities and the overall health status were similar. CONCLUSION: Employment status at the time of transplantation and in post-transplant period has a strong and independent association with the graft and recipient survival. Full time employment at the time of transplant and at one-yr post-transplant is associated with lower risk for graft failure and recipient mortality. However, working beyond the time covered by Medicare might be associated with potential risk for graft survival.

Factors affecting kidney-transplant outcome in recipients with lupus nephritis.

BACKGROUND: Factors associated with outcome in renal transplant recipients with lupus nephritis have not been studied. METHODS: Using the data from the United States Renal Data System of patients transplanted between January 1, 1995 through December 31, 2002 (and followed through December 31, 2003) (n = 2882), we performed a retrospective analysis of factors associated with long-term death-censored graft survival and recipient survival. RESULTS: The number of pretransplant pregnancies incrementally increased the risk of graft failure [hazard ratio (HR) 1.54, p < 0.05] in the entire subgroup of females and in the subgroup of recipients aged 25-35 yr. Recipient and donor age had an association with both the risk of graft failure (HR 0.96, p < 0.001; HR 1.01, p < 0.005) and recipient death (HR 1.04, p < 0.001; HR 1.01, p < 0.05). Greater graft-failure risk accompanied increased recipient weight (HR 1.01, p < 0.001); African Americans compared with whites (HR 1.55, p < 0.001); greater Charlson comorbidity index (HR 1.17, p < 0.05); and greater panel reactive antibody (PRA) levels (HR 1.06, p < 0.001). Pretransplant peritoneal dialysis as the predominant modality had an association with decreased risk of graft failure (HR 0.49, p < 0.001), while prior transplantation was associated with greater risk of graft failure and recipient death (HR 2.29, p < 0.001; HR 3.59, p < 0.001, respectively) compared with hemodialysis (HD). The number of matched human leukocyte antigens (HLA) antigens and living donors (HR 0.92, p < 0.05; HR 0.64, p < 0.001, respectively) was associated with decreased risk of graft failure. Increased risk of graft failure and recipient death was associated with nonuse of calcineurin inhibitors (HR 1.89, p < 0.005; HR 1.80, p < 0.005) and mycophenolic acid (MPA) (including mycophenolate mofetil and MPA) or azathioprine (HR 1.41, p < 0.05; HR 1.66, p < 0.01). Using both cyclosporine and tacrolimus was associated with increased risk of graft failure (HR 2.09, p < 0.05). Using MPA is associated with greater risk of recipient death compared with azathioprine (HR 1.47, p < 0.05). CONCLUSION: In renal transplant recipients with lupus nephritis, multiple pregnancies, multiple blood transfusions, greater comorbidity index, higher body weight, age and African American race of the donor or recipient, prior history of transplantation, greater PRA levels, lower level of HLA matching, deceased donors, and HD in pretransplant period have an association with increased risk of graft failure. Similarly, higher recipient and donor age, prior transplantations, and higher rate of pretransplant transfusions are associated with greater risk of recipient mortality. Using neither cyclosporine nor tacrolimus or using both (compared with tacrolimus) and neither MPA nor azathioprine (compared with azathioprine) was associated with increased risk of graft failure and recipient death. Using MPA is associated with greater risk of recipient death compared with azathioprine. Testing these results in a prospective study might provide important information for clinical practice.

Effect of donors' intravenous drug use, cigarette smoking, and alcohol dependence on kidney transplant outcome.

BACKGROUND: The shortage of organ donors for kidney transplants has made the expansion of the kidney donor pool a clinically significant issue. Previous studies suggest that kidneys from donors with a history of intravenous (IV) drug, cigarette, and/or alcohol use are considered to be a risky choice. However, these kidneys could potentially be used and expand the kidney supply pool if no evidence shows their association with adverse transplant outcomes. METHODS: This study analyzed the United Network for Organ Sharing dataset from 1994 to 1999 using Kaplan-Meier survival analysis and Cox modeling. The effects on transplant outcome (graft and recipient survival) were examined with respect to the donors' IV drug use, cigarette smoking, and alcohol dependency. Covariates including the recipient variables, the donor variables, and the transplant procedure variables were included in the Cox models. RESULTS: The results show that the donors' history of cigarette smoking is a statistically significant risk factor for both graft survival (hazard ratio=1.05, P<0.05) and recipient survival (1.06, P<0.05), whereas neither IV drug use nor alcohol dependency had significant adverse impact on graft or recipient survival. CONCLUSIONS: Assuming that adequate testing for potential infections is performed, there is no evidence to support avoiding the kidneys from donors with IV drug use or alcohol dependency in transplantation. Utilizing these kidneys would clearly expand the potential pool of donor organs.

Predicting three-year kidney graft survival in recipients with systemic lupus erythematosus.

Predicting the outcome of kidney transplantation is important in optimizing transplantation parameters and modifying factors related to the recipient, donor, and transplant procedure. As patients with end-stage renal disease (ESRD) secondary to lupus nephropathy are generally younger than the typical ESRD patients and also seem to have inferior transplant outcome, developing an outcome prediction model in this patient category has high clinical relevance. The goal of this study was to compare methods of building prediction models of kidney transplant outcome that potentially can be useful for clinical decision support. We applied three well-known data mining methods (classification trees, logistic regression, and artificial neural networks) to the data describing recipients with systemic lupus erythematosus (SLE) in the US Renal Data System (USRDS) database. The 95% confidence interval (CI) of the area under the receiver-operator characteristic curves (AUC) was used to measure the discrimination ability of the prediction models. Two groups of predictors were selected to build the prediction models. Using input variables based on Weka (a open source machine learning software) supplemented with additional variables of known clinical relevance (38 total predictors), the logistic regression performed the best overall (AUC: 0.74, 95% CI: 0.72-0.77)-significantly better (p < 0.05) than the classification trees (AUC: 0.70, 95% CI: 0.67-0.72) but not significantly better (p = 0.218) than the artificial neural networks (AUC: 0.71, 95% CI: 0.69-0.73). The performance of the artificial neural networks was not significantly better than that of the classification trees (p = 0.693). Using the more parsimonious subset of variables (six variables), the logistic regression (AUC: 0.73, 95% CI: 0.71-0.75) did not perform significantly better than either the classification tree (AUC: 0.70, 95% CI: 0.68-0.73) or the artificial neural network (AUC: 0.73, 95% CI: 0.70-0.75) models. We generated several models predicting 3-year allograft survival in kidney transplant recipients with SLE that potentially can be used in practice. The performance of logistic regression and classification tree was not inferior to more complex artificial neural network. Prediction models may be used in clinical practice to identify patients at risk.

Predicting kidney transplant survival using tree-based modeling.

Predicting the outcome of kidney transplantation is clinically important and computationally challenging. The goal of this project was to develop the models predicting probability of kidney allograft survival at 1, 3, 5, 7, and 10 years. Kidney transplant data from the United States Renal Data System (January 1, 1990, to December 31, 1999, with the follow-up through December 31, 2000) were used (n = 92,844). Independent variables included recipient demographic and anthropometric data, end-stage renal disease course, comorbidity information, donor data, and transplant procedure variables. Tree-based models predicting the probability of the allograft survival were generated using roughly two-thirds of the data (training set), with the remaining one-third left aside to be used for models validation (testing set). The prediction of the probability of graft survival in the independent testing dataset achieved a good correlation with the observed survival (r = 0.94, r = 0.98, r = 0.99, r = 0.93, and r = 0.98) and relatively high areas under the receiving operator characteristic curve (0.63, 0.64, 0.71, 0.82, and 0.90) for 1-, 3-, 5-, 7-, and 10-year survival prediction, respectively. The models predicting the probability of 1-, 3-, 5-, 7-, and 10-year allograft survival have been validated on the independent dataset and demonstrated performance that may suggest implementation in clinical decision support system.

The impact of recipient history of cardiovascular disease on kidney transplant outcome.

Cardiovascular disease (CVD) leads to increased mortality rates among renal transplant recipients; however, its effect on allograft survival has not been well studied. The records from the United States Renal Data System and the United Network for Organ Sharing from January 1, 1995, through December 31, 2002, were examined in this retrospective study. The outcome variables were allograft survival time and recipient survival time. The primary variable of interest was CVD, defined as the presence of at least one of the following: cardiac arrest, myocardial infarction, dysrhythmia, congestive heart failure, ischemic heart disease, peripheral vascular disease, and unstable angina. The Cox models were adjusted for potential confounding factors. Of the 105,181 patients in the data set, 20,371 had a diagnosis of CVD. The presence of CVD had an adverse effect on allograft survival time (HR 1.12, p < 0.001) and recipient survival time (HR 1.41, p < 0.001). Among the subcategories, congestive heart failure (HR 1.14, p < 0.005) and dysrhythmia (HR 1.26, p < 0.05) had adverse effects on allograft survival time. In addition to increasing mortality rates, CVD at the time of end-stage renal disease onset is also a significant risk factor for renal allograft failure. Further research is needed to evaluate the role of specific forms of CVD in allograft and recipient outcome.

The association between recipient alcohol dependency and long-term graft and recipient survival.

BACKGROUND: The causative role of alcohol consumption in renal disease is controversial, and its effect on renal graft and recipient survival has not been previously studied. METHODS: We analysed the association between pre-transplant [at the time of end-stage renal disease (ESRD) onset] alcohol dependency and renal graft and recipient survival. The United States Renal Data System (USRDS) records of kidney transplant recipients 18 years or older transplanted between 1 January 1995 and 31 December 2002 were examined. We used Kaplan-Meier analysis and Cox regression models adjusted for covariates to analyse the association between pre-transplant alcohol dependency and graft and recipient survival. RESULTS: In an entire study cohort of 60 523, we identified 425 patients with a history of alcohol dependency. Using Cox models, alcohol dependency was found to be associated with increased risk of death-censored graft failure [hazard ratio (HR) 1.38, P < 0.05] and increased risk of transplant recipient death (HR 1.56, P < 0.001). Subgroup analysis demonstrated an association of alcohol-dependency with recipient survival and death-censored graft survival in males (but not in females), and in both white and non-white racial subgroups. CONCLUSIONS: We concluded that alcohol dependency at the time of ESRD onset is a risk factor for renal graft failure and recipient death.

Role of pre-transplant marital status in renal transplant outcome.

BACKGROUND: End-stage renal disease is associated with illness-induced disruptions that challenge patients and their families to accommodate and adapt. However, the impact of patients' marital status on kidney transplant outcome has never been studied. This project, based on data from United States Renal Data System (USRDS), helps to answer how marriage affects renal transplant outcome. METHODS: Data have been collected from USRDS on all kidney/kidney-pancreas allograft recipients between January 1, 1995 and June 30, 2002, who were 18 yr old or older and had information about their marital status prior to the kidney transplantation (n = 2061). Survival analysis was performed using Kaplan-Meier methods and Cox proportional hazards modeling to control for confounding variables. RESULTS: Overall findings of this study suggest that being married has a significant protective effect on death-censored graft survival [Hazard Ratio (HR) 0.80, p < 0.05] but a non-significant effect on recipient survival (HR 0.85, p = 0.122). When stratified by gender, the effect was still present in males for death-censored graft survival (HR 0.75, p < 0.05), but not for recipient survival (HR 0.86, p = 0.24). The effect was not observed in females, where neither graft (HR 0.90, p = 0.55) nor recipient (HR 0.8, p = 0.198) survival had an association with marital status. In subgroup analysis similar association was found in the recipients of a single transplant. CONCLUSION: Based on our analysis, being married in the pre-transplant period is associated with positive outcome for the graft, but not for the recipient survival. When analyzed separately, the effect is present in male, but not in female recipients.

Role of socioeconomic status in kidney transplant outcome.

There is controversy regarding the influence of genetic versus environmental factors on kidney transplant outcome in minority groups. The goal of this project was to evaluate the role of certain socioeconomic factors in allograft and recipient survival. Graft and recipient survival data from the United States Renal Data System were analyzed using Cox modeling with primary variables of interest, including recipient education level, citizenship, and primary source of pay for medical service. College (hazard ratio [HR] 0.93, P < 0.005) and postcollege education (HR 0.85, P < 0.005) improved graft outcome in the whole group and in patients of white race. Similar trends were observed for recipient survival (HR 0.9, P < 0.005 for college; HR 0.88, P = 0.09 for postcollege education) in the whole population and in white patients. Resident aliens had a significantly better graft outcome in the entire patient population (HR 0.81, P < 0.001) and in white patients in subgroup analysis (HR 0.823, P < 0.001) compared with US citizens. A similar effect was observed for recipient survival. Using Medicare as a reference group, there is a statistically significant benefit to graft survival from having private insurance in the whole group (HR 0.87, P < 0.001) and in the black (HR 0.8, P < 0.001) and the white (HR 0.89, P < 0.001) subgroups; a similar effect of private insurance is observed on recipient survival in the entire group of patients and across racial groups. Recipients with higher education level, resident aliens, and patients with private insurance have an advantage in the graft and recipient outcomes independent of racial differences.

The association between length of post-kidney transplant hospitalization and long-term graft and recipient survival.

BACKGROUND: There has been a general trend towards shortened length of post-kidney transplant hospitalization (LOH). The decision regarding patients's discharge from the hospital theoretically may be based on several factors, including, but not limited to, patient well being, insurance status, family situation and other, mostly socio-economic factors, as opposed to hard medical evidence. However, the appropriate LOH in kidney transplant recipients is not well studied regarding long-term outcomes. METHODS: This study retrospectively analysed the association between LOH and graft and recipient survival based on United States Renal Data System dataset. In total, 100,762 patients who underwent transplant during 1995-2002 were included. Kaplan-Meier survival analysis and Cox models were applied to the whole patient cohort and on sub-groups stratified by the presence of delayed graft function, patient comorbidity index and donor type (deceased or living). RESULTS: In recipient survival, both short (<4 d) and long (>5 d) LOH showed a significant adverse effect (p < 0.01) on survival times. In the analysis of graft survival, long LOH (>or=2 wk) also showed significant adverse effects (p < 0.001) on survival times. However, short LOH (<4 d) did not reach statistical significance, although it was still associated with adverse effects on graft survival. These observations were consistent across the whole patient cohort and sub-groups stratified by the presence of delayed graft function, patient comorbidity index and donor type. CONCLUSION: Clinical considerations should be used to make the decision regarding appropriate time of post-kidney transplant recipient discharge. Based on this study, shorter than four d post-kidney transplant hospitalization may potentially be harmful to long-term graft and recipient survival.