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.

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.

The association of lipid-modifying medications with mortality in patients on long-term peritoneal dialysis.

BACKGROUND: The effect of lipid-lowering therapy on clinical outcomes in peritoneal dialysis patients has not been carefully addressed. STUDY DESIGN: Secondary analysis of a retrospective cohort study. SETTING & PARTICIPANTS: Data from 1,053 incident peritoneal dialysis patients from the US Renal Data System prospective Dialysis Morbidity and Mortality Wave 2 study. PREDICTOR: Use of lipid-modifying medications (93% statins, 7% other medications). OUTCOMES & MEASUREMENTS: Cox regression with propensity score adjustment was used to evaluate time to cardiovascular or all-cause mortality during a 2-year follow-up period. Subgroups based on predefined cutoff values for serum total cholesterol or triglycerides, presence of diabetes, and comorbidity index were analyzed separately. RESULTS: Use of lipid-modifying medications was associated with decreased all-cause (hazard ratio [HR], 0.74; 95% confidence interval, 0.56 to 0.98) and cardiovascular (HR, 0.67; 95% confidence interval, 0.47 to 0.95) mortality compared with no use of lipid-modifying medications. In subgroup analyses, use of lipid-modifying medications was associated with decreased all-cause mortality (HR, 0.46; 95% confidence interval, 0.22 to 0.95) in the subgroups with cholesterol levels of 226 to 275 mg/dL (HR, 0.27; 95% confidence interval, 0.09 to 0.80) and cholesterol levels greater than 275 mg/dL and cardiovascular mortality (HR, 0.31; 95% confidence interval, 0.11 to 0.85) in the subgroup with cholesterol levels of 226 to 275 mg/dL. Use of lipid-modifying medications also was associated with decreased cardiovascular mortality (HR, 0.64; 95% confidence interval, 0.41 to 0.99) in patients with diabetes and decreased all-cause (HR, 0.65; 95% confidence interval, 0.45 to 0.94) and cardiovascular mortality (HR, 0.55; 95% confidence interval, 0.35 to 0.87) in those with Charlson Comorbidity Index score higher than 2. LIMITATIONS: Observational study with retrospective design. Considerable amount of missing data and limited amount of information for the extreme values of cholesterol and triglycerides. CONCLUSIONS: These observational data suggest that lipid-modifying medication therapy may be associated with improved clinical outcomes in peritoneal dialysis patients.

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.

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.

The role of pre-emptive re-transplant in graft and recipient outcome.

BACKGROUND: The effect of the pre-emptive re-transplant, and of inter-transplant waiting time generally, on graft and recipient survival is not well established. METHODS: Analysis of the United States Renal Data System (USRDS) data (1/1/90 through 12/31/00; n = 92,844) was performed. Cox regression was used to analyse time to event, with an additional analysis to stratify by transplant era. RESULTS: Having a prior transplant, as well as the total number of transplants, was related to an increased risk of graft failure [hazard ratio (HR) 1.24, P<0.001 for history of prior transplant; HR 1.35 per transplant, P<0.001], but not to recipient death. The time waiting for re-transplant slightly worsened the risk for recipient mortality in the entire patient population and in the recipients of single re-transplant (HR 1.003 and 1.004 per month respectively, P<0.001), and for graft failure only in recipients of single re-transplant (HR 1.001 per month, P<0.05). Pre-emptive re-transplant (dialysis-free re-transplant or transplant within 6 days of last graft failure) increased the risk of graft failure (HR 1.36, P<0.001) and did not have any statistically significant effect on recipient survival. The longer duration of prior graft survival but not the type of the graft (living vs deceased) had protective effect on the consecutive graft and recipient survival. CONCLUSIONS: With the potential caveats associated with retrospective data analysis, these results suggest that pre-emptive re-transplantation is associated with increased risk of graft failure, while longer time on dialysis in between transplants is associated with negative effect upon graft and recipient survival in most patient subgroups. The optimal time in between graft failure and re-transplant was not evaluated in this study. Further prospective studies might be needed to confirm the observed effects.

Role of maintenance immunosuppressive regimen in kidney transplant outcome.

Data of long-term immunosuppressive protocol comparison are lacking. The goal of this study was to compare kidney transplant outcome using three common immunosuppressive protocols. A retrospective study was performed of the graft and recipient survival using US Renal Data System data (n = 31,012) between January 1, 1995, and December 31, 1999, with the follow-up through December 31, 2000, on prednisone + cyclosporine + mycophenolate mofetil (PCM; n = 17,108), prednisone + tacrolimus + mycophenolate mofetil (PTM; n = 7225), or prednisone + cyclosporine + azathioprine (PCA; n = 6679). Compared with PCM, there is an increased risk for allograft failure associated with PTM (hazard ratio [HR] 1.09; P < 0.05) and PCA (HR 1.15; P < 0.001). Similar associations were demonstrated in the following subgroups: Early (before 1997) and late (in or after 1997) transplant periods, in living-donor transplants, and in adult and kidney-only recipients. This association also was found between PCA regimen and graft survival in the entire patient population (HR 1.15; P < 0.001) and in the studied subgroups. PCA (HR 1.15; P < 0.005), but not PTM (HR 1.01; P = 0.816), regimen was associated with increased recipient mortality in the entire patient population and in patient subgroups. Secondary outcomes (serum creatinine values at given time points, acute rejection rate, and posttransplantation malignancies) are also discussed. These data suggest that a PCM regimen is associated with lower risk for graft failure compared with a PTM regimen and with lower risk for graft failure and recipient death compared with a PCA regimen.

Duration of end-stage renal disease and kidney transplant outcome.

BACKGROUND: Patients nearing end-stage renal disease (ESRD) increasingly choose pre-emptive renal transplant (PRT) to avoid pre-transplant dialysis and to minimize ESRD. Compared with long-term dialysis, PRT has been shown to increase allograft survival. However, the merit of short-term dialysis is not well characterized, and it may be the better medical choice in some patients. The goal of the study was to characterize the relationship between the duration of dialysis vs allograft and patient survival. METHODS: We performed a retrospective nationwide cohort study of all kidney transplants (Tx) between January 1, 1990 and December 31, 1999, with a follow-up period through December 31, 2000. Participants were identified using the United States Renal Data System (USRDS), which tracks all ESRD cases in the nation including patients on dialysis and with kidney Tx. Patients with the history of more than one kidney Tx were excluded. Allograft survival and recipient survival were the primary outcomes of this study. Duration of ESRD as a continuous variable as well as divided into categories (14 days, 15-60 days, 61-180 days, 181-365 days, 1-2 years, 2-3 years, 3-5 years and >5 years) was the primary risk factor of interest. Models were adjusted for multiple donor and recipient factors, including demographics and co-morbidities, as well as for Tx procedure characteristics. RESULTS: A total of 81,130 patient records were used for analysis (age 44.1+/-14.3 years, 61% males, 24% black, 29% diabetic, pre-transplant ESRD duration 27.1+/-26.4 months, 26% living donors). ESRD duration, as a continuous variable, is associated with a modest increase in the risk of graft failure over time [hazard ratio (HR) 1.02 per year of ESRD duration, P<0.001]. When ESRD is studied as a categorical variable (duration of 0-14 days vs longer durations), the increased risk of allograft failure reached statistical significance only when the time on dialysis was > or =181 days. The duration of ESRD was a significant risk for recipient death (HR 1.04 per year, P<0.001); however, mortality risk reached statistical significance only when the patient had been on dialysis for > or =1 year. CONCLUSIONS: This study of USRDS records suggests that a short (<6 months) dialysis course has no detrimental effect on graft and patient survival, and should not be deferred if medically indicated.