Association Between Donor-Recipient Biological Relationship and Allograft Outcomes After Living Donor Kidney Transplant

Developing a genetic testing panel for evaluation of morbidities in kidney transplant recipients

Cardiovascular disease, infection, malignancy, and thromboembolism are major causes of morbidity and mortality in kidney transplant recipients (KTR). Prospectively identifying monogenic conditions associated with post-transplant complications may enable personalized management. Therefore, we developed a transplant morbidity panel (355 genes) associated with major post-transplant complications including cardiometabolic disorders, immunodeficiency, malignancy, and thrombophilia. This gene panel was then evaluated using exome sequencing data from 1590 KTR. Additionally, genes associated with monogenic kidney and genitourinary disorders along with American College of Medical Genetics (ACMG) secondary findings v3.2 were annotated. Altogether, diagnostic variants in 37 genes associated with Mendelian kidney and genitourinary disorders were detected in 9.9% (158/1590) of KTR; 25.9% (41/158) had not been clinically diagnosed. Moreover, the transplant morbidity gene panel detected diagnostic variants for 56 monogenic disorders in 9.1% KTRs (144/1590). Cardiovascular disease, malignancy, immunodeficiency, and thrombophilia variants were detected in 5.1% (81), 2.1% (34), 1.8% (29) and 0.2% (3) among 1590 KTRs, respectively. Concordant phenotypes were present in half of these cases. Reviewing implications for transplant care, these genetic findings would have allowed physicians to set specific risk factor targets in 6.3% (9/144), arrange intensive surveillance in 97.2% (140/144), utilize preventive measures in 13.2% (19/144), guide disease-specific therapy in 63.9% (92/144), initiate specialty referral in 90.3% (130/144) and alter immunosuppression in 56.9% (82/144). Thus, beyond diagnostic testing for kidney disorders, sequence annotation identified monogenic disorders associated with common post-transplant complications in 9.1% of KTR, with important clinical implications. Incorporating genetic diagnostics for transplant morbidities would enable personalized management in pre- and post-transplant care.

Pregnancy after deceased donor vs living donor kidney transplant: associated obstetric and graft outcomes

BACKGROUND

Outside of pregnancy, recipients of a deceased donor kidney transplant experience worse graft and overall survival compared with recipients of a living donor kidney transplant. In pregnancy, it is unknown whether the type of donor graft modifies either graft health in the peripartum period or pregnancy outcomes.

OBJECTIVE

This study aimed to define characteristics and outcomes in pregnancy based on donor type in kidney transplant recipients.

STUDY DESIGN

This was a retrospective cohort study of adult kidney transplant recipients who received their graft between 2000 and 2019 with a subsequent pregnancy enrolled in the Transplant Pregnancy Registry International. The primary outcome was graft loss within 2 years of delivery. The secondary outcomes included severe maternal morbidity and neonatal composite morbidity. Univariate, multivariable logistic regression, and Cox proportional-hazards models were constructed for statistical analysis, with recipients of a living unrelated donor as the referent.

RESULTS

Overall, 638 pregnant patients after kidney transplant had pregnancy outcomes that met our inclusion criteria. Of these patients, 168 (26.3%) received a graft from a deceased donor, 310 (48.6%) received a graft from a living related donor, and 160 (25.1%) received a graft from a living unrelated donor. Recipients of a deceased donor were more likely to be nulliparous, have an unplanned pregnancy, and self-identify as non-White. Moreover, recipients of a deceased donor were more likely to experience urinary tract infections (deceased donor: 21.8%; living related donor: 10.1%; living unrelated donor: 20.6%; P=.018). Severe maternal morbidity (deceased donor: 3.4%; living related donor: 2.8%; living unrelated donor: 7.2%) and neonatal composite morbidity (deceased donor: 8.4%; living related donor: 17.1%; living unrelated donor: 14.4%) did not differ by donor type. Deceased donor transplant was associated with graft loss within 2 years of delivery (deceased donor: 6.7%; living related donor: 3.7%; living unrelated donor: 1.3%; adjusted odds ratio, 7.52; 95% confidence interval, 1.53-60.8) and long-term graft loss from transplant (adjusted hazard ratio, 2.08; 95% confidence interval, 1.10-3.95).

CONCLUSION

Although our study demonstrated an association between deceased donor transplant and graft loss after pregnancy, it did not provide evidence that pregnancy itself causes graft loss. Recipients of a deceased donor kidney transplant should not be discouraged from pursuing pregnancy based on their donor type, but these patients should undergo preconception counseling with a discussion of their individualized obstetrical and graft risks, close intrapartum monitoring for infection and hypertensive disease, and continued surveillance for at least 2 years after delivery with a multidisciplinary obstetrics and transplant team.

Racial Equity in Living Donor Kidney Transplant Centers, 2008-2018

Importance

It is unclear whether center-level factors are associated with racial equity in living donor kidney transplant (LDKT).

Objective

To evaluate center-level factors and racial equity in LDKT during an 11-year time period.

Design, Setting, and Participants

A retrospective cohort longitudinal study was completed in February 2023, of US transplant centers with at least 12 annual LDKTs from January 1, 2008, to December 31, 2018, identified in the Health Resources Services Administration database and linked to the US Renal Data System and the Scientific Registry of Transplant Recipients.

Main Outcomes and Measures

Observed and model-based estimated Black-White mean LDKT rate ratios (RRs), where an RR of 1 indicates racial equity and values less than 1 indicate a lower rate of LDKT of Black patients compared with White patients. Estimated yearly best-case center-specific LDKT RRs between Black and White individuals, where modifiable center characteristics were set to values that would facilitate access to LDKT.

Results

The final cohorts of patients included 394 625 waitlisted adults, of whom 33.1% were Black and 66.9% were White, and 57 222 adult LDKT recipients, of whom 14.1% were Black and 85.9% were White. Among 89 transplant centers, estimated yearly center-level RRs between Black and White individuals accounting for center and population characteristics ranged from 0.0557 in 2008 to 0.771 in 2018. The yearly median RRs ranged from 0.216 in 2016 to 0.285 in 2010. Model-based estimations for the hypothetical best-case scenario resulted in little change in the minimum RR (from 0.0557 to 0.0549), but a greater positive shift in the maximum RR from 0.771 to 0.895. Relative to the observed 582 LDKT in Black patients and 3837 in White patients, the 2018 hypothetical model estimated an increase of 423 (a 72.7% increase) LDKTs for Black patients and of 1838 (a 47.9% increase) LDKTs for White patients.

Conclusions and Relevance

In this cohort study of patients with kidney failure, no substantial improvement occurred over time either in the observed or the covariate-adjusted estimated RRs. Under the best-case hypothetical estimations, modifying centers' participation in the paired exchange and voucher programs and increased access to public insurance may contribute to improved racial equity in LDKT. Additional work is needed to identify center-level and program-specific strategies to improve racial equity in access to LDKT.

Association of Primary Kidney Disease Type and Donor Relatedness With Live Donor Kidney Transplant Outcomes: An Analysis of ANZDATA

RATIONALE & OBJECTIVE

There is limited information about the association between primary kidney disease and donor relatedness with transplant outcomes. This study addresses this gap by evaluating clinical outcomes after kidney transplantation in recipients of living donor kidneys as a function of primary kidney disease type and donor relatedness in Australia and New Zealand.

STUDY DESIGN

Retrospective observational study.

SETTING & PARTICIPANTS

Kidney transplant recipients who received allografts from living donors between January 1, 1998, and December 31, 2018, as recorded in the Australian and New Zealand Dialysis and Transplant Registry (ANZDATA).

EXPOSURES

Primary kidney disease type categorized as majority monogenic, minority monogenic, or other primary kidney disease based on disease heritability as well as donor relatedness.

OUTCOME

Primary kidney disease recurrence, graft failure.

ANALYTICAL APPROACH

Kaplan-Meier analysis and Cox proportion hazards regression to generate hazard ratios for primary kidney disease recurrence, allograft failure, and mortality. Partial likelihood ratio test was used to examine possible interactions between primary kidney disease type and donor relatedness for both study outcomes.

RESULTS

Among 5,500 live donor kidney transplant recipients, majority monogenic (adjusted HR, 0.58, P<0.001) and minority monogenic primary kidney diseases (adjusted HR, 0.64, P<0.001) were associated with reduced primary kidney disease recurrence compared with other primary kidney diseases. Majority monogenic primary kidney disease was also associated with reduced allograft failure (adjusted HR, 0.86, P=0.04) compared with other primary kidney diseases. Donor relatedness was not associated with primary kidney disease recurrence nor graft failure. No interaction was detected between primary kidney disease type and donor relatedness for either study outcome.

LIMITATIONS

Potential misclassification of primary kidney disease type, incomplete ascertainment of primary kidney disease recurrence, unmeasured confounding.

CONCLUSIONS

Monogenic primary kidney disease is associated with lower rates of primary kidney disease recurrence and allograft failure. Donor relatedness was not associated with allograft outcomes. These results may inform pretransplant counseling and live donor selection.

PLAIN-LANGUAGE SUMMARY

There are theoretical concerns that live-donor kidney transplants may be associated with increased risks of kidney disease recurrence and transplant failure due to unmeasurable shared genetic factors between the donor and the recipient. This study analyzed data from the Australia and New Zealand Dialysis and Transplant (ANZDATA) registry and showed that, although disease type was associated with the risk of disease recurrence and transplant failure, donor relatedness did not impact transplant outcomes. These findings may inform pretransplant counseling and live donor selection.

Living Donor Kidney Transplant in Recipients With Glomerulonephritis: Donor Recipient Biologic Relationship and Allograft Outcomes

Using the Scientific Registry of Transplant Recipients, we examined the association between donor-recipient biologic relationship and long-term recipient and allograft survival among glomerulonephritis (GN) patients. Four GN types were studied: membranous nephropathy, IgA, lupus-associated nephritis, and focal segmental glomerulosclerosis (FSGS). We identified all adult primary living-donor recipients between 2000 and 2018 (n = 19,668): related (n = 10,437); unrelated (n = 9,231). Kaplan-Meier curves were generated for the recipient, death-censored graft survival and death with functioning graft through ten years post-transplant. Multivariable Cox proportional hazard models were used to examine the association between the donor-recipient relationship and outcomes of interest. There was an increased risk for acute rejection by 12 months post-transplant among the unrelated compared to the related group in IgA (10.1% vs. 6.5%, p<0.001), FSGS (12.1% vs. 10%, p-0.016), and lupus nephritis (11.8% vs. 9.2%; p-0.049). The biological donor-recipient relationship was not associated with a worse recipient or graft survival or death with functioning graft in the multivariable models. These findings are consistent with the known benefits of living-related-donor kidney transplants and counter the reports of the potential adverse impact of the donor-recipient biologic relationship on allograft outcomes.

Strategies to Overcome HLA Sensitization and Improve Access to Retransplantation after Kidney Graft Loss

An increasing number of patients waitlisted for kidney transplantation have a previously failed graft. Retransplantation provides a significant improvement in morbidity, mortality, and quality of life when compared to dialysis. However, HLA sensitization is a major barrier to kidney retransplantation and the majority of the highly sensitized patients are waiting for a subsequent kidney transplant. A multidisciplinary team that includes immunogeneticists, transplant nephrologists and surgeons, and adequate allocation policies is fundamental to increase access to a kidney retransplant. A review of Pubmed, ScienceDirect, and the Cochrane Library was performed on the challenges of kidney retransplantation after graft loss, focusing on the HLA barrier and new strategies to overcome sensitization. Conclusion: Technical advances in immunogenetics, new desensitization protocols, and complex allocation programs have emerged in recent years to provide a new hope to kidney recipients with a previously failed graft.

Vignette-Based Reflections to Inform Genetic Testing Policies in Living Kidney Donors

Family history of kidney disease increases risk of end-stage kidney disease (ESKD) in donors. Pre-donation genetic testing is recommended in evaluation guidelines and regulatory policy. Collaborating across several institutions, we describe cases to illustrate the utility as well as practical issues in incorporating genetic testing in transplant protocols. Case 1 is from 2009, before pervasive genetic testing. A healthy 27-year-old Caucasian male had an uneventful donor evaluation for his mother, who had early onset ESKD of unclear cause. He participated in paired-exchange kidney donation, but developed progressive kidney disease and gout over the next 10 years. A uromodulin gene mutation (NM_003361.3(UMOD):c.377 G>A p.C126Y) was detected and kidney biopsy showed tubulointerstitial kidney disease. The patient subsequently required kidney transplantation himself. Case 2 was a 36-year-old African American female who had an uneventful kidney donor evaluation. She underwent gene panel-based testing to rule out ApolipoproteinL1 risk variants, for which was negative. Incidentally, a sickle-cell trait (NM_000518.5(HBB):c.20A>T p.Glu7Val) was noted, and she was declined for kidney donation. This led to significant patient anguish. Case 3 was a 26-year-old Caucasian female who underwent panel-based testing because the potential recipient, her cousin, carried a variant of uncertain significance in the hepatocyte nuclear factor-1-β (HNF1B) gene. While the potential donor did not harbor this variant, she was found to have a likely pathogenic variant in complement factor I (NM_000204.4(CFI):c.1311dup:p.Asp438Argfs*8), precluding kidney donation. Our cases emphasize that while genetic testing can be invaluable in donor evaluation, transplant centers should utilize detailed informed consent, develop care pathways for secondary genetic findings, and share experience to develop best practices around genetic testing in donors.

How good is a living donor? Systematic review and meta-analysis of the effect of donor demographics on post kidney transplant outcomes

Background and Aims

Living donor kidneys are considered the best quality organs. In the attempt to expand the donor pool, the donor’s age, sex and body mass index (BMI) might be considered as potential determinants of the kidney transplant outcomes, and thus guide recipient selection. We aimed to investigate the effects of donor demographics on kidney function, graft and recipient survival, delayed graft function (DGF) and acute rejection (AR).

Methods

Systematic review and meta-analysis. EMBASE, MEDLINE, Web of Science, BIOSIS, CABI, SciELO and Cochrane were searched using algorithms. NHBLI tools were used for risk of bias assessment. Mean difference (MD), standardized mean difference (SMD), and risk ratio (RR) were calculated in Revman 5.4

Results

Altogether, 5129 studies were identified by the search algorithm; 47 studies met the inclusion criteria and were analyzed. No significant difference in recipient 1-year survival was found between recipients of donors aged < 50 vs donors aged > 50 (RR = 0.65 95% CI: 0.1–4.1), and recipients of donors aged < 60 vs donors aged > 60 (RR = 0.81 95% CI: 0.3–2.3). Graft survival was significantly higher in recipients of grafts from donors aged < 60. Risk of AR (RR = 0.62 95% CI: 0.5–0.8) and DGF (RR = 0.28 95% CI: 0.1–0.9) were significantly lower in recipients of grafts from donors aged < 60. One-year serum creatinine was significantly lower in recipients from donors aged < 60 years compared to donors aged > 60 years (MD = 0.3 mg/dl 95% CI: 0.1–0.9), although there was high heterogeneity. Recipients of grafts from male donors had lower 1-year serum creatinine (MD = 0.12 mg/dl 95% CI: 0.2–0.1) and higher eGFR compared to recipients of female donors (p < 0.00001). Donor obesity increased the incidence of delayed graft function but not acute rejection (RR = 0.66 95% CI: 0.32–1.34).

Conclusions

Older donor age was associated with worse post-transplant outcomes and recipients of male donors had better 1-year eGFR. Donor obesity affects the incidence of delayed graft function, but not the incidence of acute rejection in recipients.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-021-01231-7.

Racial disparities in living donor kidney transplantation in the United States

Living donor kidney transplant (LDKT) is the best treatment for end-stage kidney disease, but there are racial disparities in LDKT rates. To study putative mechanisms of these disparities, we identified 58 752 adult kidney transplant candidates first activated on the United States kidney transplant waitlist 2015-2016 and defined four exposure groups by race/primary payer: African American/Medicaid, African American/NonMedicaid, Non-African American/Medicaid, Non-African American/NonMedicaid. We performed competing risk regression to compare risk of LDKT between groups. Among included candidates, 30% had African American race and 9% had Medicaid primary payer. By the end of follow up, 16% underwent LDKT. The cumulative incidence of LDKT was lowest for African American candidates regardless of payer. Compared to African American/Non-Medicaid candidates, the adjusted likelihood of LDKT was higher for both Non-African American/Medicaid (HR 1.60, 95%CI 1.43-1.78) and Non-African American/Non-Medicaid candidates (HR 2.66, 95%CI 2.50-2.83). Results were similar when analyzing only candidates still waitlisted > 2 years after initial activation or candidates with type O blood. Among 9639 candidates who received LDKT, only 13% were African American. Donor-recipient relationships were similar for African American and Non-African American recipients. These findings indicate African American candidates have a lower incidence of LDKT than candidates of other races, regardless of primary payer.