Effect of ethnicity on outcome of simultaneous pancreas and kidney transplantation

Simpson's paradox and the impact of donor-recipient race-matching on outcomes post living or deceased donor kidney transplantation in the United States

Background

Race is a prognostic indicator in kidney transplant (KT). However, the effect of donor-recipient race-matching on survival after KT remains unclear.

Methods

Using the United Network for Organ Sharing (UNOS) database, a retrospective study was conducted on 244,037 adults who received first-time, kidney-alone transplantation between 2000 and 2019. All patients were categorized into two groups according to donor-recipient race-matching, and the living and deceased donor KT (LDKT and DDKT) were analyzed in subgroups.

Results

Of the 244,037 patients, 149,600 (61%) were race-matched, including 107,351 (87%) Caucasian, 20,741 (31%) African Americans, 17,927 (47%) Hispanics, and 3,581 (25%) Asians. Compared with race-unmatching, race-matching showed a reduced risk of overall mortality and graft loss (unadjusted hazard ratio (HR) 0.86, 95% confidence interval (CI) 0.84-0.87; and unadjusted HR 0.79, 95% CI: 0.78-0.80, respectively). After propensity score-matching, donor-recipient race-matching was associated with a decreased risk of overall graft loss (P < 0.001) but not mortality. In subgroup analysis, race-matching was associated with higher crude mortality (HR 1.12, 95% CI: 1.06-1.20 in LDKT and HR 1.11, 95% CI: 1.09-1.14 in DDKT). However, race-matching was associated with a decreased risk of graft loss in DDKT (unadjusted HR 0.97, 95% CI: 0.96-0.99), but not in LDKT. After propensity score-matching, race-matching had better outcomes for LDKT (patient survival, P = 0.047; graft survival, P < 0.001; and death-censored graft survival, P < 0.001) and DDKT (death-censored graft survival, P = 0.018). Nonetheless, race-matching was associated with an increased adjusted mortality rate in the DDKT group (P < 0.001).

Conclusion

Race-matching provided modest survival advantages after KT but was not enough to influence organ offers. Cofounding factors at baseline led to a contorted crude conclusion in subgroups, which was reversed again to normal trends in the combined analysis due to Simpson's paradox caused by the LDKT/DDKT ratio.

Pancreas Transplantation in Minorities including Patients with a Type 2 Diabetes Phenotype

Background: Prior to year 2000, the majority of pancreas transplants (PTx) were performed as simultaneous pancreas-kidney transplants (SPKTs) in Caucasian adults with end stage renal failure secondary to type 1 diabetes mellitus (T1DM) who were middle-aged. In the new millennium, improving outcomes have led to expanded recipient selection that includes patients with a type 2 diabetes mellitus (T2DM) phenotype, which excessively affects minority populations. Methods: Using PubMed® to identify appropriate citations, we performed a literature review of PTx in minorities and in patients with a T2DM phenotype. Results: Mid-term outcomes with SPKT in patients with uremia and circulating C-peptide levels (T2DMphenotype) are comparable to those patients with T1DM although there may exist a selection bias in the former group. Excellent outcomes with SPKT suggests that the pathophysiology of T2DM is heterogeneous with elements consisting of both insulin deficiency and resistance related to beta-cell failure. As a result, increasing endogenous insulin (Cp) production following PTx may lead to freedom checking blood sugars or taking insulin, better metabolic counter-regulation, and improvements in quality of life and life expectancy compared to other available treatment options. Experience with solitary PTx for T2DM or in minorities is limited but largely mirrors the trends reported in SPKT. Conclusions: PTx is a viable treatment option in patients with pancreas endocrine failure who are selected appropriately regardless of diabetes type or recipient race. This review will summarize data that unconventional patient populations with insulin-requiring diabetes may gain value from PTx with an emphasis on contemporary experiences and appropriate selection in minorities in the new millennium.

Simultaneous pancreas‐kidney transplantation in Caucasian versus African American patients: Does recipient race influence outcomes?

The influence of African American (AA) recipient race on outcomes following simultaneous pancreas‐kidney transplantation (SPKT) is uncertain.

Race does not predict pancreas graft failure after pancreas transplantation in the Modern Era

BACKGROUND

African-American (AA) has historically been associated with inferior graft survival after pancreas transplantation. However, with the improvement of immunosuppression and surgical technique, we hypothesized that the racial disparity has been neutralized.

METHODS

We analyzed data from the Scientific Registry of Transplant Recipients (1989-2018). Using Kaplan-Meier estimation and Cox proportional hazards regression, we examined the influence of race on pancreatic graft survival.

RESULTS

Before 2009, AA recipients had a higher risk of pancreatic graft failure after adjusting for confounding factors (hazard ratio [HR]: 1.16, 95% confidence interval [CI]: 1.08-1.24), but the risks for Hispanic and Asian recipients were both comparable to their Caucasian counterparts. However, the risk of pancreatic graft failure in AA recipients dropped to 1% and was no longer significant since 2009 (HR: 1.01, 95%CI: 0.88-1.16). Interestingly, donor race showed similar results. Furthermore, the concordance statistic of the complete pancreas donor risk index (including donor race) was 0.582, whereas the concordance did not change when donor race was eliminated from the model.

CONCLUSIONS

AA and other races have shown similar pancreatic graft survival in the modern era. Furthermore, donor racial disparity also seems neutralized; thus, donor race should not be considered as an indicator of pancreatic donor quality. This article is protected by copyright. All rights reserved.

The impact of race on metabolic, graft, and patient outcomes after pancreas transplantation

BACKGROUND

Racial disparities following pancreas transplantation (PTX) are poorly defined.

METHODS

This was a large-scale, single-center, longitudinal cohort study including adult PTX recipients. Patients were grouped by race to allow for comparisons.

RESULTS

287 PTX recipients were included; 125 (43.5%) were African American (AA). At baseline, AAs had a significantly higher proportion of T2DM (19.4% vs. 5.7%, p = 0.001), were younger, and more likely to be female. AAs experienced significantly higher rates of pancreatic leaks and post-operative bleeding. PTX rejection was comparable, however, kidney rejection tended to be higher among AA SPKs. Long-term mean HgbA1C levels were significantly higher among AAs (6.9% vs. 6.3%, p = 0.039). Patient and graft survival was comparable between groups, but early patient survival tended to be lower in AAs.

CONCLUSIONS

This study demonstrated significant perioperative health disparities among AA PTX recipients, including poorer glycemic control and more early deaths, despite similar long-term patient and graft survival.

Simultaneous Pancreas and Kidney Transplantation is Associated With Inferior Long-Term Outcomes in African Americans

OBJECTIVES

Simultaneous pancreas and kidney transplant (SPK) is the most effective treatment for patients with type 1 diabetes mellitus and renal failure. However, the effect of ethnicity on SPK outcomes is not well understood.

METHODS

We studied the influence of recipient ethnicity on SPK using the United Network for Organ Sharing database. A retrospective review of 20,196 SPK patients from 1989 to 2014 was performed. The recipients were divided into 4 groups: 15,833 whites (78.40%), 2708 African Americans (AA) (14.39%), 1456 Hispanics (7.21%), and 199 Asians (0.99%).

RESULTS

Hispanics and Asians experienced the best overall graft and patient outcomes. Both groups demonstrated significantly superior graft and patient survival rates compared with whites at 1, 3, 5, 10, and 15 years (all P < 0.0001). African Americans experienced significantly superior 1- and 3-year patient survival compared with whites (both P < 0.0001). African Americans also experienced significantly superior 1-year kidney and pancreas graft survival compared with whites (P < 0.0001). However, AA experienced significantly inferior patient and allograft outcomes for all other time points compared with whites.

CONCLUSIONS

Based on United Network for Organ Sharing data from 1989 to 2014, AA have worse long-term patient and graft survival rates compared with whites, Hispanics, and Asians undergoing SPK.

Influence of recipient race on the outcome of simultaneous pancreas and kidney transplantation

Racial differences on the outcome of simultaneous pancreas and kidney (SPK) transplantation have not been well studied. We compared mortality and graft survival of African Americans (AA) recipients to other racial/ethnic groups (non-AA) using the national data. We studied a total of 6585 adult SPK transplants performed in the United States between January 1, 2000 and December 31, 2007. We performed multivariate logistic regression analyses to determine risk factors associated with early graft failure and immune-mediated late graft loss. We used conditional Kaplan-Meier survival and multivariate Cox regression analyses to estimate late death-censored kidney and pancreas graft failure and death between the groups. Although there was no racial disparity in the first 90 days, AA patients had 38% and 47% higher risk for late death-censored kidney and pancreas graft failure, respectively (p = 0.006 and 0.001). AA patients were twice more likely to lose the kidney and pancreas graft due to rejection (OR 2.31 and 1.86, p = 0.002 and 0.008, respectively). Bladder pancreas drainage was associated with inferior patient survival (HR 1.42, 95% CI 1.15, 1.75, p = 0.001). In the era of modern immunosuppression, AA SPK transplant patients continue to have inferior graft outcome. Additional studies to explore the mechanisms of such racial disparity are warranted.

Access and outcomes among minority transplant patients, 1999-2008, with a focus on determinants of kidney 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.

A comparison of long-term survivals of simultaneous pancreas-kidney transplant between African American and Caucasian recipients with basiliximab induction therapy

African Americans (AA) have traditionally been thought to have higher immunologic risk than Caucasians (CA) for rejection and allograft loss. The impact of ethnicity on the outcome of simultaneous pancreas-kidney (SPK) transplant with basiliximab induction has not been reported. In this study, we retrospectively analyze the long-term results of 36 AA and 55 CA recipients of primary SPK. The actual patient survival rates of AA and CA groups were 91.7% vs. 90.1% at 1 year, 93.3% vs. 88.1% at 3 years, and 94.4% vs. 83.3% at 5 years. The actual kidney survival of AA and CA were 91.7% vs. 89.1% at 1 year, 90% vs. 81% at 3 years, and 83.3% vs. 75% at 5 years. The actual pancreas survival of AA and CA were 88.9% vs. 85.5% at 1 year, 83.3% vs. 78.6% at 3 years and 72.2% vs. 70.8% at 5 years. Death-censored analyses also found no difference in pancreas and kidney graft survival rates over 5 years. Higher rejection rate, but the same low CMV infection, and comparable quality of graft function were noted in AA group. AA may not have worse long-term outcomes than CA recipients of SPK with basiliximab induction and tacrolimus (TAC), mycophenolate acid (MFA) and steroid maintenance immunotherapy.

Long-term graft function after allogeneic islet transplantation

Islet transplants are emerging as a viable option for the treatment of type 1 diabetes mellitus. From 1989 to 1995 we conducted a series of simultaneous islet-kidney transplants in six uremic type 1 diabetic patients. We report two of these patients who have shown persistent islet graft function over many years. Two female patients with duration of diabetes of 27 and 37 years underwent simultaneous islet-kidney transplant under steroid- and cyclosporine-based immunosuppression. Freshly isolated islets were supplemented with cryopreserved islets from our low-temperature bank of frozen islets. A total islet mass of 9,866 and 15,061 islet equivalents/kg body weight, respectively, was transplanted into the liver through portal vein. Reasonable blood glucose control has been achieved for up to 6 years posttransplant in one patient, but there was minimum clinical benefit from the islet graft at 10 years. In contrast, sustained insulin secretion with nearly normal HbA1c at 13 years follow-up was observed in another patient, providing hope for improving long-term graft outcomes for islet transplant recipient.

Inferior Late Functional and Metabolic Outcomes in African American Simultaneous Kidney-Pancreas Recipients

The aim of this study was to determine the impact of ethnicity on the major endpoints of a prospective, multi-center, randomized trial of 2 dosing regimens of daclizumab compared with no antibody induction in simultaneous kidney-pancreas transplantation (SKPT). A total of 298 patients were randomized into 3 groups: daclizumab 1 mg/kg/dose every 14 days for 5 doses (Group I, n = 107), daclizumab 2 mg/kg/dose every 14 days for 2 doses (Group II, n = 113), and no antibody induction (Group III, n = 78). All patients received tacrolimus (TAC), mycophenolate mofetil (MMF), and steroids. Thirty-seven patients (12.4%) were African American (AA) and 261 were non-African American (NAA). Demographic and transplant characteristics were comparable between AA and NAA patients. At 3 years, there were no differences in patient, kidney, or pancreas graft survival rates. Rejection rate was similar between AA and NAA. Although mean serum creatinine (SCr) levels at 1 year were comparable between AA and NAA patients (AA 1.5 mg/dL vs NAA 1.3 mg/dL; P = .23), by 3 years AA patients had higher mean SCr levels (AA 2.1 mg/dL vs NAA 1.5 mg/dL; P < .0001) and lower calculated glomerular filtration rate (GFR) (AA 45 mL/min vs NAA 56 mL/min; P = .01). Mean HgbA1C, total cholesterol, and diastolic blood pressure (BP) were higher in AA patients at 3 years, compared with NAA patients. In conclusion, in this study, AA patients had worse late functional and metabolic outcomes after SKPT compared with NAA patients. Further longitudinal follow-up is needed to determine the ultimate impact of these findings on long-term patient and graft survival.

Who among cytomegalovirus-seropositive liver transplant recipients is at risk for cytomegalovirus infection?

A vast majority of the transplant recipients are cytomegalovirus (CMV)-seropositive (R+). We sought to assess variables predictive of CMV infection, specifically in R+ liver transplant recipients. Study patients comprised 182 consecutive liver transplant recipients who survived at least 14 days after transplantation. Surveillance testing was used to detect CMV infection. Pre-emptive therapy was employed for the prevention of CMV disease, however, no antiviral prophylaxis was used for CMV infection. CMV infection developed in 32.5% (38 of 117) of R+ patients, 84.6% (33 of 39) of R-/D+, and 3.8% (1 of 26) of R-/D- patients. In R+ patients, Hispanic race (21.6% vs. 7.8%, P = 0.06), donor CMV seropositivity (73.7% vs. 45.6%, P = 0.005), and hepatocellular carcinoma (23.7% vs. 6.3%, P = 0.05) correlated with a higher risk of CMV infection. In a multivariate model, Hispanic race (OR: 3.5, 95% CI: 1.03-11.6, P = 0.045), donor CMV serostatus (OR: 4.0, 95% CI: 1.6-10.2, P = 0.003) and hepatocellular carcinoma (OR: 5.8, 95% CI: 1.6-20.5, P = 0.006) were all significant independent predictors of CMV infection. The aforementioned variables did not portend a higher risk of CMV infection in R-/D+ patients; donor CMV seropositivity overwhelmed all other risk factors in R- patients (P < 0.00001). In conclusion, CMV-seropositive liver transplant recipients at risk for CMV infection can be identified based on readily assessable variables. Preventive strategies may be selectively targeted toward these patients.