A Safe Anti-A2 Titer for a Successful A2 Incompatible Kidney Transplantation: A Single-center Experience and Review of the Literature

Outcomes of A2/A2B to B Deceased Donor Kidney Transplantation: A Retrospective Study

Background A2/A2B to B kidney transplantation has the potential to increase transplant access for traditionally disadvantaged blood group B minority candidates. Despite prior reports of positive post-transplant safety and clinical success, A2/A2B to B kidney transplantation remains underutilized in the United States. This study aims to investigate the post-transplant outcomes of A2/A2B to B kidney transplants performed at our center. Methods A retrospective study of all A2/A2B to B deceased donor kidney transplants (DDKTs) at our center from 2017 through 2023 was performed. Recipient and donor demographics, recipient medical history, time to transplant from listing, and post-transplant clinical outcomes were assessed, including one-year graft and patient survival. Results Of the 54 A2/A2B to B DDKTs performed during this period, 36 recipients were male, and 18 were female. The mean recipient age was 53.2 years. There were 22 (40.7%) African American recipients, 12 (22.2%) Hispanic recipients, 11 (20.3%) Caucasian recipients, eight (14.8%) Asian recipients, and one (1.8%) recipient of "other" race. The mean estimated post-transplant survival score was 46.5%. The mean donor age was 40.2 years, and the mean kidney donor profile index score was 44%. The mean time from waitlisting to transplant was 216 days. Delayed graft function was observed in five (9.2%) patients. Three (5.5%) patients had biopsy-proven acute rejection in the first year after transplant. The mean serum creatinine at one-year post-transplant was 1.4 mg/dL. At one-year post-transplant, graft survival was 96.2%, and patient survival was 98.1%. Conclusions Our study demonstrated excellent one-year post-transplant graft and patient survival rates with A2/A2B to B DDKT, with minority candidates predominantly benefiting from this.

A2/A2B Deceased Donor Kidney Transplantation Using A2 Titers Improves Access to Kidney Transplantation: A Single-Center Study

Rationale & Objective

The option for A2/A2B deceased donor kidney transplantation was integrated into the kidney allocation system in 2014 to improve access for B blood group waitlist candidates. Despite excellent reported outcomes, center uptake has remained low across the United States. Here, we examined the effect of implementing an A2/A2B protocol using a cutoff titer of ≤1:8 for IgG and ≤1:16 for IgM on blood group B kidney transplant recipients at a single center.

Study Design

Retrospective observational study.

Setting & Participants

Blood group B recipients of deceased donor kidney transplants at a single center from January 1, 2019, to December 2022.

Exposure

Recipients of deceased donor kidney transplants were analyzed based on donor blood type with comparisons of A2/A2B versus blood group compatible.

Outcomes

One-year patient survival, death-censored allograft function, primary nonfunction, delayed graft function, allograft function as measured using serum creatinine levels and estimated glomerular filtration rate at 1 year, biopsy-proven rejection, and need for plasmapheresis.

Analytical Approach

Comparison between the A2/A2B and compatible groups were performed using the Fisher test or the χ2 test for categorical variables and the nonparametric Wilcoxon rank-sum test for continuous variables.

Results

A total of 104 blood type B patients received a deceased donor kidney transplant at our center during the study period, 49 (47.1%) of whom received an A2/A2B transplant. Waiting time was lower in A2/A2B recipients compared with blood group compatible recipients (57.9 months vs 74.7 months, P = 0.01). A2/A2B recipients were more likely to receive a donor after cardiac death (24.5% vs 1.8%, P < 0.05) and experience delayed graft function (65.3% vs 41.8%). There were no observed differences in the average serum creatinine level or estimated glomerular filtration rate at 1 month, 3 months, and 1 year post kidney transplantation, acute rejection, or primary nonfunction.

Limitations

Single-center study. Small cohort size limiting outcome analysis.

Conclusions

Implementation of an A2/A2B protocol increased transplant volumes of blood group B waitlisted patients by 83.6% and decreased the waiting time for transplantation by 22.5% with similar transplant outcomes.

Expanding the access to kidney transplantation: Strategies for kidney transplant programs

Kidney transplantation is the most successful kidney replacement therapy available, resulting in improved recipient survival and societal cost savings. Yet, nearly 70 years after the first successful kidney transplant, there are still numerous barriers and untapped opportunities that constrain the access to transplant. The literature describing these barriers is extensive, but the practices and processes to solve them are less clear. Solutions must be multidisciplinary and be the product of strong partnerships among patients, their networks, health care providers, and transplant programs. Transparency in the referral, evaluation, and listing process as well as organ selection are paramount to build such partnerships. Providing early culturally congruent and patient-centered education as well as maximizing the use of local resources to facilitate the transplant work up should be prioritized. Every opportunity to facilitate pre-emptive kidney transplantation and living donation must be taken. Promoting the use of telemedicine and kidney paired donation as standards of care can positively impact the work up completion and maximize the chances of a living donor kidney transplant.

A2/A2B to B deceased donor kidney transplantation in the Kidney Allocation System era

Kidney transplantation from blood type A2/A2B donors to type B recipients (A2→B) has increased dramatically under the current Kidney Allocation System (KAS). Among living donor transplant recipients, A2-incompatible transplants are associated with an increased risk of all-cause and death-censored graft failure. In light of this, we used data from the Scientific Registry of Transplant Recipients from December 2014 until June 2022 to evaluate the association between A2→B listing and time to deceased donor kidney transplantation (DDKT) and post-DDKT outcomes for A2→B recipients. Among 53 409 type B waitlist registrants, only 12.6% were listed as eligible to accept A2→B offers ("A2-eligible"). The rates of DDKT at 1-, 3-, and 5-years were 32.1%, 61.4%, and 72.1% among A2-eligible candidates and 14.1%, 29.9%, and 44.1% among A2-ineligible candidates, with the former experiencing a 133% higher rate of DDKT (Cox weighted hazard ratio (wHR) = 2.192.332.47; P < .001). The 7-year adjusted mortality was comparable between A2→B and B-ABOc (type B/O donors to B recipients) recipients (wHR 0.780.941.13, P = .5). Moreover, there was no difference between A2→B vs B-ABOc DDKT recipients with regards to death-censored graft failure (wHR 0.771.001.29, P > .9) or all-cause graft loss (wHR 0.820.961.12, P = .6). Following its broader adoption since the implementation of the kidney allocation system, A2→B DDKT appears to be a safe and effective transplant modality for eligible candidates. As such, A2→B listing for eligible type B candidates should be expanded.

A2/A2B to B kidney transplantation outcomes: A single center 7-year experience

INTRODUCTION

Data on long-term outcomes following A2/A2B to B kidney transplants since the 2014 kidney allocation system (KAS) changes are few. The primary aim of this study is to report our 7-year experience with A2/A2B to B kidney transplants and to compare post-transplant outcomes of A2/A2B to a concurrent group of B to B kidney transplants. Additionally, the study evaluates the impact of pre-transplant anti-A1 titers on survival outcomes in A2/A2B transplants.

METHODS

This retrospective, single-center analysis included all adults who received A2/A2B to B deceased donor kidney transplants from December 2014 to June 2021 compared to B to B recipients. The effects of pre-transplant IgM/IgG titers, stratified as ≤1:8 and ≥1:16, on death-censored, rejection-free, and overall graft survival were tested.

RESULTS

Fifty-three A2/A2B and 114 B to B adults were included with a median follow-up time of 32 months. Overall graft survival, patient survival, and rejection-free graft survival did not differ between the two groups. There were no differences between the groups' overall kidney function values (p > .80) or their temporal trajectories (time by group interaction p > .11). Unadjusted death-censored graft survival was lower in A2/A2B to B compared to B recipients (p = .03), but the effect was not significant (p = .195) after adjusting for any readmissions (p = .96), rejection episodes (p < .001) or BK infection (p = .76). We did not detect an effect of pre-transplant titer group on death-censored (p = .59), rejection-free (p = .61), or overall graft survival (p = .26) CONCLUSIONS: A2/A2B to B kidney transplants have comparable overall patient and graft survival, rejection-free graft survival, and longitudinal renal function compared to B to B transplants at our center. Allograft survival outcomes were not significantly different between patients with low and high pre-transplant anti-A1 IgM/IgG titers.

The real unmet need: A multifactorial approach for identifying sensitized kidney candidates with low access to transplant

BACKGROUND

At the start of 2020, the kidney waiting list consisted of 2526 candidates with a calculated panel reactive antibody (CPRA) of 99.9% or greater, a cohort demonstrated in published research to have meaningfully lower than average access to transplantation even under the revised kidney allocation system (KAS).

METHODS

This was a retrospective analysis of US kidney registrations using data from the OPTN [Reference (https://optn.transplant.hrsa.gov/data/about-data/)]. The period-prevalent study cohort consisted of US kidney-alone registrations who waited at least 1 day between April 1, 2016, when HLA DQ-Alpha and DP-Beta unacceptable antigen data became available in OPTN data collection, to December 31, 2019. Poisson rate regression was used to model deceased donor kidney transplant rates per active year waiting and using an offset term to account for differential at-risk periods. Median time to transplant was estimated for each IRR group using the Kaplan-Meier method. Sensitivity analyses were included to address geographic variation in supply-to-demand ratios and differences in dialysis time or waiting time.

RESULTS

In this study, we found 1597 additional sensitized (CPRA 50-<99.9%) candidates with meaningfully lower than average access to transplant when simultaneously taking into account CPRA and other factors. In combination with CPRA, candidate blood type, Estimated Post-Transplant Survival Score (EPTS), and presence of other antibody specificities beyond those in the current, 5-locus CPRA were found to influence the likelihood of transplant.

CONCLUSION

In total, this suggests approximately 4100 sensitized candidates are on the waiting list who represent a community of disadvantaged patients who may benefit from progressive therapies and interventions to facilitate incompatible transplantation. Though associated with higher risks, such interventions may nevertheless be more attractive than remaining on dialysis with the associated accumulation of mortality risk over time.