Use of Machine Learning Consensus Clustering to Identify Distinct Subtypes of Black Kidney Transplant Recipients and Associated Outcomes

Importance: Among kidney transplant recipients, Black patients continue to have worse graft function and reduced patient and graft survival. Better understanding of different phenotypes and subgroups of Black kidney transplant recipients may help the transplant community to identify individualized strategies to improve outcomes among these vulnerable groups. Objective: To cluster Black kidney transplant recipients in the US using an unsupervised machine learning approach. Design, Setting, and Participants: This cohort study performed consensus cluster analysis based on recipient-, donor-, and transplant-related characteristics in Black kidney transplant recipients in the US from January 1, 2015, to December 31, 2019, in the Organ Procurement and Transplantation Network/United Network for Organ Sharing database. Each cluster\u27s key characteristics were identified using the standardized mean difference, and subsequently the posttransplant outcomes were compared among the clusters. Data were analyzed from June 9 to July 17, 2021. Exposure: Machine learning consensus clustering approach. Main Outcomes and Measures: Death-censored graft failure, patient death within 3 years after kidney transplant, and allograft rejection within 1 year after kidney transplant. Results: Consensus cluster analysis was performed for 22 687 Black kidney transplant recipients (mean [SD] age, 51.4 [12.6] years; 13 635 men [60%]), and 4 distinct clusters that best represented their clinical characteristics were identified. Cluster 1 was characterized by highly sensitized recipients of deceased donor kidney retransplants; cluster 2, by recipients of living donor kidney transplants with no or short prior dialysis; cluster 3, by young recipients with hypertension and without diabetes who received young deceased donor transplants with low kidney donor profile index scores; and cluster 4, by older recipients with diabetes who received kidneys from older donors with high kidney donor profile index scores and extended criteria donors. Cluster 2 had the most favorable outcomes in terms of death-censored graft failure, patient death, and allograft rejection. Compared with cluster 2, all other clusters had a higher risk of death-censored graft failure and death. Higher risk for rejection was found in clusters 1 and 3, but not cluster 4. Conclusions and Relevance: In this cohort study using an unsupervised machine learning approach, the identification of clinically distinct clusters among Black kidney transplant recipients underscores the need for individualized care strategies to improve outcomes among vulnerable patient groups

Outcomes of Kidney Transplant Recipients with Sickle Cell Disease: An Analysis of the 2000–2019 UNOS/OPTN Database

Background: Lower patient survival has been observed in sickle cell disease (SCD) patients who go on to receive a kidney transplant. This study aimed to assess the post-transplant outcomes of SCD kidney transplant recipients in the contemporary era. Methods: We used the OPTN/UNOS database to identify first-time kidney transplant recipients from 2010 through 2019. We compared patient and allograft survival between recipients with SCD (n = 105) vs. all other diagnoses (non-SCD, n = 146,325) as the reported cause of end-stage kidney disease. We examined whether post-transplant outcomes improved among SCD in the recent era (2010–2019), compared to the early era (2000–2009). Results: After adjusting for differences in baseline characteristics, SCD was significantly associated with lower patient survival (HR 2.87; 95% CI 1.75–4.68) and death-censored graft survival (HR 1.98; 95% CI 1.30–3.01), compared to non-SCD recipients. The lower patient survival and death-censored graft survival in SCD recipients were consistently observed in comparison to outcomes of recipients with diabetes, glomerular disease, and hypertension as the cause of end-stage kidney disease. There was no significant difference in death censored graft survival (HR 0.99; 95% CI 0.51–1.73, p = 0.98) and patient survival (HR 0.93; 95% CI 0.50–1.74, p = 0.82) of SCD recipients in the recent versus early era. Conclusions: Patient and allograft survival in SCD kidney recipients were worse than recipients with other diagnoses. Overall SCD patient and allograft outcomes in the recent era did not improve from the early era. The findings of our study should not discourage kidney transplantation for ESKD patients with SCD due to a known survival benefit of transplantation compared with remaining on dialysis. Urgent future studies are needed to identify strategies to improve patient and allograft survival in SCD kidney recipients. In addition, it may be reasonable to assign risk adjustment for SCD patients

Zero-mismatch deceased-donor kidney versus simultaneous pancreas-kidney transplantation.

BackgroundPatients with type 1 diabetes mellitus (T1DM) and end-stage renal disease may receive a simultaneous pancreas-kidney (SPK), living-donor kidney (LDK), or deceased-donor kidney (DDK) with possible pancreas after kidney transplantation. SPK is associated with superior patient and kidney graft survival compared with DDK, whereas SPK and LDK have comparable outcomes. It is unclear whether SPK and LDK offer a survival benefit over zero-mismatch (0MM) DDK. In this study, we compared the outcomes of T1DM recipients using data from the Organ Procurement and Transplant Network/United Network for Organ Sharing.MethodsAdult (≥18 years) first-time transplant recipients with T1DM waitlisted for SPK and transplanted from 1995 to 2010 were included in this study. Patient and death-censored kidney graft survival were compared between 0MMDDK (n=228), mismatched (MM) DDK (n=964), 0MMSPK (n=215), MMSPK (n=11951), 2 haplotype identical (2hap) LDK (n=205), and non-2hapLDK (n=1719) recipients. Multivariate analysis was performed using stepwise Cox proportional hazards models.ResultsAt 7 years, patient and death-censored graft survival of 0MMDDK recipients (85% and 81%, respectively) were not statistically different from that of 0MMSPK (81% and 85%; log-rank P value vs. 0MMDDK, 0.17 and 0.48, respectively) and 2hapLDK recipients (89% and 86%; log-rank P value vs. 0MMDDK, 0.34 and 0.18, respectively). Among all groups, MMDDK showed the worst patient survival (71%; log-rank P value vs. 0MMDDK, 0.001)ConclusionPatient and kidney graft survival of 0MMDDK recipients were comparable to both SPK and LDK recipients. These findings suggest that T1DM patients awaiting SPK may consider accepting a 0MMDDK if an offer is available

Outcomes of Kidney Transplant Patients with Atypical Hemolytic Uremic Syndrome Treated with Eculizumab: A Systematic Review and Meta-Analysis

Background: Kidney transplantation in patients with atypical hemolytic uremic syndrome (aHUS) is frequently complicated by recurrence, resulting in thrombotic microangiopathy in the renal allograft and graft loss. We aimed to assess the use of eculizumab in the prevention and treatment of aHUS recurrence after kidney transplantation. Methods: Databases (MEDLINE, EMBASE and Cochrane Database) were searched through February 2019. Studies that reported outcomes of adult kidney transplant recipients with aHUS treated with eculizumab were included. Estimated incidence rates from the individual studies were extracted and combined using random-effects, generic inverse variance method of DerSimonian and Laird. Protocol for this systematic review has been registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42018089438). Results: Eighteen studies (13 cohort studies and five case series) consisting of 380 adult kidney transplant patients with aHUS who received eculizumab for prevention and treatment of post-transplant aHUS recurrence were included in the analysis. Among patients who received prophylactic eculizumab, the pooled estimated incidence rates of recurrent thrombotic microangiopathy (TMA) after transplantation and allograft loss due to TMA were 6.3% (95%CI: 2.8–13.4%, I2 = 0%) and 5.5% (95%CI: 2.9–10.0%, I2 = 0%), respectively. Among those who received eculizumab for treatment of post-transplant aHUS recurrence, the pooled estimated rates of allograft loss due to TMA was 22.5% (95%CI: 13.6–34.8%, I2 = 6%). When the meta-analysis was restricted to only cohort studies with data on genetic mutations associated with aHUS, the pooled estimated incidence of allograft loss due to TMA was 22.6% (95%CI: 13.2–36.0%, I2 = 10%). We found no significant publication bias assessed by the funnel plots and Egger’s regression asymmetry test (p > 0.05 for all analyses). Conclusions: This study summarizes the outcomes observed with use of eculizumab for prevention and treatment of aHUS recurrence in kidney transplantation. Our results suggest a possible role for anti-C5 antibody therapy in the prevention and management of recurrent aHUS

Kidney failure requiring kidney transplantation after pancreas transplant alone.

Pancreas transplant alone (PTA) is usually performed in type 1 diabetic patients with preserved renal function to correct severe metabolic complications. One of the major concerns is renal failure after PTA. Here, we reported the cumulative incidence of kidney failure requiring kidney transplantation (KF/KT) among PTA recipients in the United States. Using the Organ Procurement Transplant Network/ United Network for Organ Sharing database, all primary adult PTA recipients with estimated baseline glomerular filtration rate (by the Modification of Diet in Renal Disease equation) >or=60 mL/min/1.73m2 were selected (n=1085). KF/ KT after PTA was defined as: wait-listing for or receiving a kidney alone (KA) or simultaneous pancreas kidney (SPK) transplant. The median follow-up time was 1185 days (25-75%: 524-2183). Ten years post PTA, 120 (11.1%) patients developed KF/KT; of those, 70 (6.5%) subsequently received a KA/SPK transplant (56 received KA and 14 received SPK) and 50 (4.6%) recipients were listed without receiving a transplant. The cumulative incidence of KF/KT after PTA at 1, 3, and 5 years after PTA was 0.3, 2.5, and 9.7%, respectively. In conclusion, KF/KT after PTA was not uncommon (9.7% at 5 years), and prospective PTA recipients should be aware of the risks of kidney failure after transplantation

Subarachnoid Hemorrhage in Hospitalized Renal Transplant Recipients with Autosomal Dominant Polycystic Kidney Disease: A Nationwide Analysis

Background: This study aimed to evaluate the hospitalization rates for subarachnoid hemorrhage (SAH) among renal transplant patients with adult polycystic kidney disease (ADPKD) and its outcomes, when compared to non-ADPKD renal transplant patients. Methods: The 2005–2014 National Inpatient Sample databases were used to identify all hospitalized renal transplant patients. The inpatient prevalence of SAH as a discharge diagnosis between ADPKD and non-ADPKD renal transplant patients was compared. Among SAH patients, the in-hospital mortality, use of aneurysm clipping, hospital length of stay, total hospitalization cost and charges between ADPKD and non-ADPKD patients were compared, adjusting for potential confounders. Results: The inpatient prevalence of SAH in ADPKD was 3.8/1000 admissions, compared to 0.9/1000 admissions in non-ADPKD patients (p < 0.01). Of 833 renal transplant patients with a diagnosis of SAH, 30 had ADPKD. Five (17%) ADPKD renal patients with SAH died in hospitals compared to 188 (23.4%) non-ADPKD renal patients (p = 0.70). In adjusted analysis, there was no statistically significant difference in mortality, use of aneurysm clipping, hospital length of stay, or total hospitalization costs and charges between ADPKD and non-ADPKD patients with SAH. Conclusion: Renal transplant patients with ADPKD had a 4-fold higher inpatient prevalence of SAH than those without ADPKD. Further studies are needed to compare the incidence of overall admissions in ADPKD and non-ADPKD patients. When renal transplant patients developed SAH, inpatient mortality rates were high regardless of ADPKD status. The outcomes, as well as resource utilization, were comparable between the two groups

Renal Transplant Outcomes in Waitlist Candidates with a Previous Inactive Status Due to Being Temporarily Too Sick.

BackgroundIn 2003, the United Network for Organ Sharing (UNOS) changed its policy to allow candidates with 'inactive' status to accrue time on the waitlist. In this study, we assessed the transplant outcomes among deceased donor kidney transplant (DDKT) recipients who were temporarily inactive specifically due to medical reason, i.e., being temporarily too sick (reason 7).MethodsUsing the UNOS database, adult DDKT recipients were divided into two groups: those who had never been inactivated (active group) and those with a history of being inactive due to reason 7 (reason 7 group). Patient and graft survival, 3-year risk of death, and graft failure were examined and compared.ResultsAfter 3 years of follow-up, patient survival in the reason 7 group was significantly lower than that of the active group (88.14% versus 91.93%, p < 0.01). The reason 7 group had a 20% increased risk of death (hazard ratio, HR 1.20, confidence interval, CI 1.04 - 1.38), a 16% increase in graft failure (HR 1.16, CI 1.06-1.28), and a 15% decrease in death-censored graft failure (HR 1.15, CI 1.01-1.31).ConclusionRecipients with a history of reason 7 have lower patient and graft survival when compared to the active group. Nonetheless, the margins of difference are minimal. Candidates with a history of reason 7 should not be discouraged from transplantation once they return to active status. Standardized criteria for placing candidates on inactive status should be developed to reduce disparities among transplant centers

Feature Importance of Acute Rejection among Black Kidney Transplant Recipients by Utilizing Random Forest Analysis: An Analysis of the UNOS Database

Background: Black kidney transplant recipients have worse allograft outcomes compared to White recipients. The feature importance and feature interaction network analysis framework of machine learning random forest (RF) analysis may provide an understanding of RF structures to design strategies to prevent acute rejection among Black recipients. Methods: We conducted tree-based RF feature importance of Black kidney transplant recipients in United States from 2015 to 2019 in the UNOS database using the number of nodes, accuracy decrease, gini decrease, times_a_root, p value, and mean minimal depth. Feature interaction analysis was also performed to evaluate the most frequent occurrences in the RF classification run between correlated and uncorrelated pairs. Results: A total of 22,687 Black kidney transplant recipients were eligible for analysis. Of these, 1330 (6%) had acute rejection within 1 year after kidney transplant. Important variables in the RF models for acute rejection among Black kidney transplant recipients included recipient age, ESKD etiology, PRA, cold ischemia time, donor age, HLA DR mismatch, BMI, serum albumin, degree of HLA mismatch, education level, and dialysis duration. The three most frequent interactions consisted of two numerical variables, including recipient age:donor age, recipient age:serum albumin, and recipient age:BMI, respectively. Conclusions: The application of tree-based RF feature importance and feature interaction network analysis framework identified recipient age, ESKD etiology, PRA, cold ischemia time, donor age, HLA DR mismatch, BMI, serum albumin, degree of HLA mismatch, education level, and dialysis duration as important variables in the RF models for acute rejection among Black kidney transplant recipients in the United States