Kidney allograft offers: Predictors of turndown and the impact of late organ acceptance on allograft survival

Impact of donor smoking history on kidney transplant recipient outcomes: A systematic review and meta-analysis

BACKGROUND

Impact of donor smoking history on kidney transplant recipient outcomes is undefined.

METHODS

We systematically searched, critically appraised, and summarized associations between donor smoking and primary outcomes of death-censored and all-cause graft failure (DCGF, ACGF), and secondary outcomes of allograft histology, delayed graft function, serum creatinine, estimated glomerular filtration rate, and mortality. We searched MEDLINE, Embase, and Cochrane Databases from 2000 to 2023. Risk of bias was assessed using Risk of Bias in Non-randomized Studies - of Exposure tool. Quality of evidence was assessed by Grading of Recommendations Assessment, Development and Evaluation Working Group recommendations. We pooled results using inverse variance, random-effects model and reported hazard ratios for time-to-event outcomes or binomial proportions. Statistical heterogeneity was assessed with I2 statistic.

RESULTS

From 1785 citations, we included 17 studies. Donor smoking was associated with modestly increased DCGF (HR 1.05 (95% CI: 1.01, 1.09); I2 = 0%; low quality of evidence), predominantly in deceased donors, and ACGF in adjusted analyses (HR 1.12 (95% CI: 1.06, 1.19); I2 = 20%; very low quality of evidence). Other outcomes could not be pooled meaningfully.

CONCLUSIONS

Kidney donor smoking history was associated with modestly increased risk of death-censored graft failure and all-cause graft failure. This review emphasizes the need for further research, standardized reporting, and thoughtful consideration of donor factors like smoking in clinical decision-making on kidney utilization and allocation.

Preoperative Risk Assessment of Early Kidney Graft Loss

Background

A large proportion of potential organ donors are not utilized for kidney transplantation out of risk of early allograft loss because of donor-related characteristics. These can be summarized using kidney donor profile index (KDPI). Because KDPI affects the choice of the recipient, the predictive ability of KDPI is tied to recipient attributes. These have been questioned to explain most of the predictive ability of KDPI. This study aims to quantify the effect of the donor on early graft loss (EGL) by accounting for nonrandom allocation.

Methods

This study included patients undergoing kidney transplantation from deceased donors between 2014 and 2020 from the Scientific Registry of Transplantation Recipients. EGL, defined as a return to dialysis or retransplantation during the first posttransplant year, was the primary endpoint. Nonrandom allocation and donor-recipient matching by KDPI necessitated the use of inverse probability treatment weighting, which served to assess the effect of KDPI and mitigate selection bias in a weighted Cox regression model.

Results

The study comprised 89 290 transplantations in 88 720 individual patients. Inverse probability treatment weighting resulted in a good balance of recipient covariates across values of continuous KDPI. Weighted analysis showed KDPI to be a significant predictor for short-term outcomes. A comparable (in terms of age, time on dialysis, previous transplants, gender, diabetes status, computed panel-reactive antibodies, and HLA mismatches) average recipient, receiving a kidney from a donor with KDPI 40-60 had a 3.5% risk of EGL increased to a risk of 7.5% if received a kidney from a KDPI >95 donor (hazard ratio, 2.3; 95% confidence interval, 1.9-2.7). However, for all-cause survival KDPI was less influential.

Conclusions

The predictive ability of KDPI does not stem from recipient confounding alone. In this large sample-sized study, modeling methods accounting for nonindependence of recipient selection verify graft quality to effectively predict short-term transplantation outcomes.

Prediction of High-Risk Donors for Kidney Discard and Nonrecovery Using Structured Donor Characteristics and Unstructured Donor Narratives

Importance

Despite the unmet need, many deceased-donor kidneys are discarded or not recovered. Inefficient allocation and prolonged ischemia time are contributing factors, and early detection of high-risk donors may reduce organ loss.

Objective

To evaluate the feasibility of machine learning (ML) and natural language processing (NLP) classification of donors with kidneys that are used vs not used for organ transplant.

Design, Setting, and Participants

This retrospective cohort study used donor information (structured donor characteristics and unstructured donor narratives) from the United Network for Organ Sharing (UNOS). All donor offers to a single transplant center between January 2015 and December 2020 were used to train and validate ML models to predict donors who had at least 1 kidney transplanted (at our center or another center). The donor data from 2021 were used to test each model.

Exposures

Donor information was provided by UNOS to the transplant centers with potential transplant candidates. Each center evaluated the donor and decided within an allotted time whether to accept the kidney for organ transplant.

Main Outcomes and Measures

Outcome metrics of the test cohort included area under the receiver operating characteristic curve (AUROC), F1 score, accuracy, precision, and recall of each ML classifier. Feature importance and Shapley additive explanation (SHAP) summaries were assessed for model explainability.

Results

The training/validation cohort included 9555 donors (median [IQR] age, 50 [36-58] years; 5571 male [58.3%]), and the test cohort included 2481 donors (median [IQR] age, 52 [40-59] years; 1496 male [60.3%]). Only 20% to 30% of potential donors had at least 1 kidney transplanted. The ML model with a single variable (Kidney Donor Profile Index) showed an AUROC of 0.69, F1 score of 0.42, and accuracy of 0.64. Multivariable ML models based on basic a priori structured donor data showed similar metrics (logistic regression: AUROC = 0.70; F1 score = 0.42; accuracy = 0.62; random forest classifier: AUROC = 0.69; F1 score = 0.42; accuracy = 0.64). The classic NLP model (bag-of-words model) showed its best metrics (AUROC = 0.60; F1 score = 0.35; accuracy = 0.59) by the logistic regression classifier. The advanced Bidirectional Encoder Representations From Transformers model showed comparable metrics (AUROC = 0.62; F1 score = 0.39; accuracy = 0.69) only after appending basic donor information. Feature importance and SHAP detected the variables (and words) that affected the models most.

Conclusions and Relevance

Results of this cohort study suggest that models using ML can be applied to predict donors with high-risk kidneys not used for organ transplant, but the models still need further elaboration. The use of unstructured data is likely to expand the possibilities; further exploration of new approaches will be necessary to develop models with better predictive metrics.

Peri-Operative Kinetics of Plasma Mitochondrial DNA Levels during Living Donor Kidney Transplantation

During ischemia and reperfusion injury (IRI), mitochondria may release mitochondrial DNA (mtDNA). mtDNA can serve as a propagator of further injury but in specific settings has anti-inflammatory capacities as well. Therefore, the aim of this study was to study the perioperative dynamics of plasma mtDNA during living donor kidney transplantation (LDKT) and its potential as a marker of graft outcome. Fifty-six donor-recipient couples from the Volatile Anesthetic Protection of Renal Transplants-1 (VAPOR-1) trial were included. Systemic venous, systemic arterial, and renal venous samples were taken at multiple timepoints during and after LDKT. Levels of mtDNA genes changed over time and between vascular compartments. Several donor, recipient, and transplantation-related variables significantly explained the course of mtDNA genes over time. mtDNA genes predicted 1-month and 24-month estimated glomerular filtration rate (eGFR) and acute rejection episodes in the two-year follow-up period. To conclude, mtDNA is released in plasma during the process of LDKT, either from the kidney or from the whole body in response to transplantation. While circulating mtDNA levels positively and negatively predict post-transplantation outcomes, the exact mechanisms and difference between mtDNA genes are not yet understood and need further exploration.

An experiment on the impact of predictive analytics on kidney offer acceptance decisions

Due to the breadth of factors that might affect kidney transplant decisions to accept an organ or wait for another, presumably "better" offer, a high degree of heterogeneity in decision-making exists among transplant surgeons and hospitals. These decisions do not typically include objective predictions regarding the future availability of equivalent or better-quality organs, nor the likelihood of patient death while waiting for another organ. To investigate the impact of displaying such predictions on organ donation decision making, we conducted a statistically designed experiment involving 53 kidney transplant professionals, where kidney organ offers were presented via an online application and systematically altered to observe effects on decision making. We found that providing predictive analytics for time-to-better offer and patient mortality improves decision consensus and decision maker confidence in their decision. Providing a visual display of the patient's mortality slope under accept/reject conditions shortened the time to decide, but did not have an impact on the decision itself. Presenting risk of death in a loss frame as opposed to a gain frame improved decision consensus and decision confidence. Patient-specific predictions surrounding future organ offers and mortality may improve decision quality, confidence, and expediency while improving organ utilization and patient outcomes.

Heart transplant offers are less likely to be accepted on weekends, holidays, and conferences

BACKGROUND

The existence of a "weekend effect" in heart transplantation (HTx) is understudied. The present study sought to determine whether the odds of (HTx) offer acceptance differed for adult and pediatric candidates depending upon the day on which the offer occurred.

METHODS

United Network for Organ Sharing data were used to identify all HTx offers to adult (listing age ≥18) and pediatric candidates from 2000-2019. Odds of offer acceptance were studied, comparing weekends, holidays, and conferences (Society of Thoracic Surgeons [STS], American Association for Thoracic Surgery [AATS], International Society for Heart and Lung Transplantation [ISHLT]) to "baseline" (all other days). Multivariable binary logistic regression analyses were performed to determine independent predictors of offer nonacceptance, controlling for the impacts of program transplant volume, region, and candidate characteristics.

RESULTS

A total of 323,953 offers occurred - 298,405 to adults and 25,548 to pediatric candidates. Clinically significant differences did not exist in donor or candidate characteristics between baseline or other events. The number of offers per day was stable throughout the year for both adults (p = 0.191) and pediatrics (p = 0.976). In adults, independently lower odds of acceptance existed on weekends (OR 0.88 [95% CI 0.84-0.92]), conferences in aggregate (0.86 [0.77-0.95]), and holidays in aggregate (0.81 [0.72-0.91]). In children, independently lower odds of acceptance were seen on weekends (0.88 [0.79-0.98]), during STS (0.46 [0.25-0.83], and during Christmas (0.32 [0.14-0.76]).

CONCLUSIONS

The day on which a HTx offer occurs significantly impacts its likelihood of acceptance. Further work can determine the impacts of human behavior or resource distribution, but knowledge of this phenomenon can inform efforts to ensure ideal organ allocation throughout the year.

Disparities in Deceased Donor Kidney Offer Acceptance: A Survey of Canadian Transplant Nephrologists, General Surgeons and Urologists

Background

Significant variability in organ acceptance thresholds have been demonstrated across the United States, but data regarding the rate and rationale for kidney donor organ decline in Canada are lacking.

Objective

To examine decision making regarding deceased kidney donor acceptance and non-acceptance in a population of Canadian transplant professionals.

Design

A survey study of theoretical deceased donor kidney cases of increasing complexity.

Setting

Canadian transplant nephrologists, urologists, and surgeons making donor call decisions responding to an electronic survey between July 22 and October 4, 2022.

Participants

Invitations to participate were distributed to 179 Canadian transplant nephrologists, surgeons, and urologists through e-mail. Participants were identified by contacting each transplant program and requesting a list of physicians who take donor call.

Measurements

Survey respondents were asked whether they would accept or decline a given donor, assuming there was a suitable recipient. They were also asked to cite reasons for donor non-acceptance.

Methods

Donor scenario-specific acceptance rates (total acceptance divided by total number of respondents for a given scenario and overall) and reasons for decline were determined and presented as a percentage of the total cases declined.

Results

In all, 72 respondents from 7 provinces completed at least one question of the survey, with considerable variability between acceptance rates for centers; the most conservative center declined 60.9% of donor cases, whereas the most aggressive center declined only 28.1%, P-value < .001. There was an increased risk of non-acceptance with advancing age, donation after cardiac death, acute kidney injury, chronic kidney disease, and comorbidities.

Limitations

As with any survey, there is the potential for participation bias. In addition, this study examines donor characteristics in isolation, however, asks respondent to assume there is a suitable candidate available. In reality, whenever donor quality is considered, it should be considered in the context of the intended recipient.

Conclusion

In a survey of increasingly medically complex deceased kidney donor cases, there was significant variability in donor decline among Canadian transplant specialists. Given relatively high rates of donor decline and apparent heterogeneity in acceptance decisions, Canadian transplant specialists may benefit from additional education regarding the benefits achieved from even medically complex kidney donors for appropriate candidates relative to remaining on dialysis on the transplant waitlist.

Revisiting the "Weekend Effect" on Adult and Pediatric Liver and Kidney Offer Acceptance

BACKGROUND Weekends can impose resource and manpower constraints on hospitals. Studies using data from prior allocation schemas showed increased adult organ discards on weekends. We examined the impact of day of the week on adult and pediatric organ acceptance using contemporary data. MATERIAL AND METHODS Retrospective analysis of UNOS-PTR match-run data of all offers for potential kidney and liver transplant from 1/1/2016 to 7/1/2021 were examined to study the rate at which initial offers were declined depending on day of the week. Risk factors for decline were also evaluated. RESULTS Of the total initial adult/pediatric liver and kidney offers, the fewest offers occurred on Mondays and Sundays. The decline rate for adult/pediatric kidneys was highest on Saturdays and lowest on Tuesdays. The decline rate for adult livers was highest on Saturday and lowest on Wednesday. In contrast, the decline rate for pediatric livers was highest on Tuesdays and lowest on Wednesdays. Independent risk factors from multivariate analysis of the adult/pediatric kidney and liver decline rate were analyzed. The weekend offer remains an independent risk factor for adult kidney and liver offer declines, but for pediatric offers, these were not significant independent risk factors. CONCLUSIONS Although allocation systems have changed, and the availability of kidneys and livers have increased in the USA over the past 5 years, the weekend effect remains significant for adult liver and kidney offers for declines. Interestingly, the weekend effect was not seen for pediatric liver and kidney offers.

Implications of Accumulated Cold Time for US Kidney Transplantation Offer Acceptance

BACKGROUND AND OBJECTIVES

Reducing discard is important for the US transplantation system because nearly 20% of the deceased donor kidneys are discarded. One cause for the discards is the avoidance of protracted cold ischemia times. Extended cold ischemia times at transplant are associated with additional risk of graft failure and patient mortality. A preference for local (within the same donor service area) or low-Kidney Donor Risk Index organs, the endogeneity of cold ischemia time during organ allocation, and the use of provisional offers all complicate the analysis of cold ischemia times' influence on kidney acceptance decision making.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using January 2018 to June 2019 Organ Procurement and Transplantation Network data, we modeled the probability of accepting an offer for a kidney after provisional acceptance. We use logistic regression that includes cold ischemia time, Kidney Donor Risk Index, and other covariates selected from literature. Endogeneity of cold ischemia time was treated by a two-stage instrumental variables approach.

RESULTS

Logistic regression results for 3.33 million provisional acceptances from 12,369 donors and 108,313 candidates quantify trade-offs between cold ischemia time at the time of offer acceptance and donor-recipient characteristics. Overall, each additional 2 hours of cold ischemia time affected acceptance for nonlocal and local recipients (odds ratio, 0.75; 95% confidence interval, 0.73 to 0.77, odds ratio, 0.88; 95% confidence interval, 0.86 to 0.91; P<0.001). For Kidney Donor Risk Index >1.75 (Kidney Donor Profile Index >85) kidneys, an additional 2 hours of cold ischemia time for nonlocal and local recipients was associated with acceptance with odds ratio, 0.58; 95% confidence interval, 0.54 to 0.63 (nonlocal) and odds ratio, 0.65; 95% confidence interval, 0.6 to 0.7 (local); P<0.001. The effect of an additional 2 hours of cold ischemia time on acceptance of kidneys with Kidney Donor Risk Index ≤1.75 (Kidney Donor Profile Index ≤85) was less pronounced for nonlocal offers (odds ratio, 0.82; 95% confidence interval, 0.80 to 0.85; P<0.001) and not significant for local offers.

CONCLUSIONS

The acceptability of marginal organs was higher when placements were nearer to the donor and when cold ischemia time was shorter.

A tool for decision-making in kidney transplant candidates with poor prognosis to receive deceased donor transplantation in the United States

The primary outcomes for kidney transplant candidates are receipt of deceased or living donor transplant, death or removal from the waiting list. Here, we conducted a retrospective analysis of national Scientific Registry of Transplant Recipients data to evaluate outcomes for 208,717 adult kidney transplant candidates following the 2014 Kidney Allocation System in the United States. Competing risks models were utilized to evaluate Time to Equivalent Risk (TiTER) of deceased donor transplantation (DDTX) and death versus waitlist removal. We also evaluated TiTER based on kidney donor profile index (KDPI) and donor age. For all groups, the cumulative incidence of DDTX was initially higher from time of listing than death or waitlist removal. However, following accrued time on the waiting list, the cumulative incidence of death or waitlist removal exceeded DDTX for certain patient groups, particularly older, diabetic, blood type B and O and shorter pre-listing dialysis time. TiTER for all candidates aged 65-69 averaged 41 months and for 70 and older patients 28 months. Overall, 39.6% of candidates were in risk groups with TiTER under 72 months and 18.5% in groups with TiTER under 24 months. Particularly for older candidates, TiTER for kidneys was substantially shorter for younger donors or lower KDPI. Thus, our findings reveal that a large proportion of waitlisted patients in the United States have poor prognoses to ever undergo DDTX and our data may improve shared decision-making for candidates at time of waitlist placement. Hence, for specific patient groups, TiTER may be a useful tool to disseminate and quantify benefits of accepting relatively high risk donor organs.

Declined Offers for Deceased Donor Kidneys Are Not an Independent Reflection of Organ Quality

Background

Deceased donor kidney offers are frequently declined multiple times before acceptance for transplantation, despite significant organ shortage and long waiting times. Whether the number of times a kidney has been declined, reflecting cumulative judgments of clinicians, is associated with long-term transplant outcomes remains unclear.

Methods

In this national, retrospective cohort study of deceased donor kidney transplants in the United States from 2008 to 2015 (n=78,940), we compared donor and recipient characteristics and short- and long-term graft and patient survival outcomes grouping by the sequence number at which the kidney was accepted for transplantation. We compared outcomes for kidneys accepted within the first seven offers in the match-run, after 8-100 offers, and for hard-to-place kidneys distinguishing those requiring >100 and >1000 offers before acceptance.

Results

Harder-to-place kidneys had lower donor quality and higher rates of delayed graft function (46% among kidneys requiring >1000 offers before acceptance versus 23% among kidneys with ≤7 offers). In unadjusted models, later sequence groups had higher hazard of all-cause graft failure, death-censored graft failure, and patient mortality; however, these associations were attenuated after adjusting for Kidney Donor Risk Index (KDRI). After adjusting for donor factors already taken into consideration during allocation, and recipient factors associated with long-term outcomes, graft, and patient survival outcomes were not significantly different for the hardest-to-place kidneys compared with the easiest-to-place kidneys, with the exception of death-censored graft failure (adjusted hazard ratio, 1.16, 95% CI, 1.05 to 1.28).

Conclusion

Late sequence offers may represent missed opportunities for earlier successful transplant for the higher-priority waitlisted candidates for whom the offers were declined.

Hardest-to-place kidney transplant outcomes in the United States

The outcomes of hardest-to-place kidney transplants-accepted last in the entire match run after being refused by previous centers-are unclear, potentially translating to risk aversion and unnecessary organ discard. We aimed to determine the outcomes of hardest-to-place kidney transplants and whether the organ acceptance position on the match run sufficiently captures the risk. This is a cohort study of the United Network for Organ Sharing data of all adult kidney-only transplant recipients from deceased donors between 2007 and 2018. Multiple regression models assessed delayed graft function, graft survival, and patient survival stratified by share type: local versus shared kidney acceptance position scaled by tertile. Among 127 028 kidney transplant recipients, 92 855 received local kidneys. The remaining received shared kidneys at sequence number 1-4 (n = 12 322), 5-164 (n = 10 485) and >164 (n = 11 366). Hardest-to-place kidneys, defined as the latest acceptance group in the match-run, were associated with delayed graft function (adjusted odds ratio 1.83, 95% confidence interval [CI] 1.74-1.92) and all-cause allograft failure (adjusted hazard ratio [aHR] 1.11, 95% CI 1.04-1.17). Results of this IRB-approved study were robust to the exclusion of operational allocation bypass and mandatory shares. The hardest-to-place kidneys accepted later in the match run were associated with higher graft failure and delayed graft function.

A machine learning approach for the prediction of overall deceased donor organ yield

BACKGROUND

Optimizing organ yield (number of organs transplanted per donor) is a potentially modifiable way to increase the number of organs available for transplant. Models to predict the expected deceased donor organ yield have been developed based on ordinary least squares regression and logistic regression. However, alternative modeling methodologies incorporating machine learning may have superior performance compared with conventional approaches.

METHODS

We evaluated the predictive accuracy of 14 machine learning models for predicting overall organ yield in a cross-validation procedure. The models were parameterized using data from the Organ Procurement and Transplantation Network database from 2000 to 2018. The inclusion criteria for the study were adult deceased donors between 18 and 84 years of age that had at least 1 organ procured for transplantation.

RESULTS

A total of 89,520 donors met the inclusion criteria. Their mean (standard deviation) age was 44 (15) years, and approximately 58% were male. Our cross-validation analysis showed that a tree-based gradient boosting model outperformed the remaining 13 models. Compared with the currently used prediction models, the gradient boosting model improves prediction accuracy by reducing the mean absolute error between 3 and 11 organs per 100 donors.

CONCLUSION

Our analysis demonstrated that the gradient boosting methodology had the best performance in predicting overall deceased donor organ yield and can potentially serve as an aid to assess organ procurement organization performance.

Prediction of Kidney Allograft Discard Before Procurement: The Kidney Discard Risk Index

OBJECTIVES

There is an 18.9% discard rate among kidney allografts. Here, we aimed to determine predictors of kidney discard and construct an index to identify high-probability discard kidney allografts prior to procurement.

MATERIALS AND METHODS

A total of 102 246 potential kidney allograft donors from the Organ Procurement and Transplantation Network database were used in this analysis. The cohort was randomized into 2 groups. The training set included 67% of the cohort and was used to derive a predictive index for discard that comprised 21 factors identified by univariate and multivariate logistic regression analysis. The validation set included 33% and was used to internally validate the kidney discard risk index.

RESULTS

In 77.3% of donors, at least 1 kidney was used for transplant, whereas in 22.7% of donors, both kidneys were discarded. The kidney discard risk index was highly predictive of discard with a C statistic of 0.89 (0.88-0.89). The bottom 10th percentile had a discard rate of 0.73%, whereas the top 10th percentile had a discard rate of 83.65%. The 3 most predictive factors for discard were age, creatinine level, and hepatitis C antibody status.

CONCLUSIONS

We identified 21 factors predictive of discard prior to donor procurement and used these to develop a kidney discard risk index with a C statistic of 0.89.

Kidney nonprocurement in solid organ donors in the United States

There are limited data on the nonprocurement of kidneys from solid organ donors. Analysis of Standard Transplant Analysis and Research files was undertaken on all deceased donors in the United States with at least 1 solid organ recovered. From 2000 to 2018, 21 731 deceased donor kidneys (averaging 1144 kidneys per year) were not procured. No kidneys were procured from 8% of liver donors, 3% of heart donors, and 3% of lung donors. Compared to donors with all kidneys procured, those with none procured were older and more likely obese, black, hypertensive, diabetic, hepatitis C positive, smokers, Public Health Service - Increased Risk designated, deceased after cardiac death, or deceased after cerebrovascular accident. Although these donors had lower quality kidneys (median Kidney Donor Risk Index (interquartile range) 1.9 (1.0) vs 1.2 (0.7)), there was substantial overlap in quality between nonprocured and procured kidneys. Nearly one third of nonprocurements were attributed to donor history. Donors with elevated terminal creatinine likely resulting from acute kidney injury (AKI) had higher odds of kidney nonprocurement. Nonprocurement odds varied widely across Organ Procurement and Transplantation Network regions, with a positive correlation between donor kidney nonprocurements and kidney discards at the donation service area level. These findings suggest current discard rates underestimate the underutilization of deceased donor kidneys and more research is needed to optimize safe procurement and utilization of kidneys from donors with AKI.

Bariatric surgery before and after kidney transplantation: long-term weight loss and allograft outcomes

BACKGROUND

Severe obesity is frequently a barrier to kidney transplantation, and kidney transplant recipients often have significant weight gain following transplantation.

OBJECTIVES

The goals of this study were to evaluate the long-term risks and benefits of bariatric surgery before and after kidney transplantation.

SETTING

University Hospital, United States.

METHODS

We performed a retrospective cohort study of 43 patients who had pretransplantation bariatric surgery and 21 patients who had posttransplantation bariatric surgery from 1994 to 2017 with propensity-score matching to identify matched controls using national registry data.

RESULTS

Body mass index at the time of transplantation was similar in patients who underwent bariatric surgery before versus after transplantation (32 versus 34 kg/m², P = .172). There was no significant difference in body mass index in the 5 years after bariatric surgery among patients who underwent bariatric surgery before versus after kidney transplantation (36 versus 32 kg/m², P = 0.814). Compared with matched controls, bariatric surgery before (n = 38) and after (n = 18) kidney transplantation was associated with a decreased risk of allograft failure (hazard ratio .31 [95% confidence interval .29-0.33] and .85 [95% confidence interval .85-.86] for pre- and posttransplant, respectively) and mortality (hazard ratio .57 [95% confidence interval .53-.61] and .80 [95% confidence interval .79-.82] for pre- and posttransplant, respectively).

CONCLUSIONS

Bariatric surgery before and after kidney transplantation results in similar maintenance of weight loss and improved long-term allograft survival compared with matched controls. Bariatric surgery appears to be a safe and reasonable approach to weight loss both before and after transplantation.

Perioperative Dexmedetomidine Improves Outcomes of Kidney Transplant

Graft function is crucial for successful kidney transplantation. Many factors may affect graft function or cause delayed graft function (DGF), which decreases the prognosis for graft survival. This study was designed to evaluate whether the perioperative use of dexmedetomidine (Dex) could improve the incidence of function of graft kidney and complications after kidney transplantation. A total of 780 patients underwent kidney transplantations, 315 received intravenous Dex infusion during surgery, and 465 did not. Data were adjusted with propensity scores and multivariate logistic regression was used. The primary outcomes are major adverse complications, including DGF and acute rejection in the early post‐transplantation phase. The secondary outcomes included length of hospital stay (LOS), infection, overall complication, graft functional status, post‐transplantation serum creatinine values, and estimated glomerular filtration rate (eGFR). Dex use significantly decreased DGF (19.37% vs. 23.66%; adjusted odds ratio, 0.744; 95% confidence interval, 0.564–0.981; P = 0.036), risk of infection, risk of acute rejection in the early post‐transplantation phase, the risk of overall complications, and LOS. However, there were no statistical differences in 90‐day graft functional status or 7‐day, 30‐day, and 90‐day eGFR. Perioperative Dex use reduced incidence of DGF, risk of infection, risk of acute rejection, overall complications, and LOS in patients who underwent kidney transplantation.

The weekend effect in kidney transplantation outcomes: a French cohort-based study

Numerous studies have reported a weekend effect on outcomes for diseases treated at hospitals. No study has been conducted in France for kidney transplantation. We therefore performed a cohort-based study to evaluate whether outcomes of kidney transplant recipients display a weekend effect. Data were extracted from the French DIVAT cohort. Patients aged 18 years and older, transplanted with a single kidney from deceased donors between 2005 and 2017 were studied. Linear regression, logistic regression, and cause-specific Cox model were used. Among the 6652 studied patients, 4653 patients were transplanted during weekdays (69.9%) versus 1999 during weekends (30.1%). The only statistically significant difference was the percentage of patients with vascular surgical complication(s) at 30 days: 13.3% in the weekend group versus 16.2% in the weekday group 0.79 (95% CI: 0.68; 0.92). We did not observe other significant differences for the other outcomes: patient or graft survival, the risk of acute rejection episodes, the 30-day percentage of urological complications, and the 1-year estimated glomerular filtration rate. Our study highlights a small protective weekend effect with less post-surgery vascular complications compared to weekdays. This paradox might be explained by a different handling of weekend transplantations.

Degree of Glomerulosclerosis in Procurement Kidney Biopsies from Marginal Donor Kidneys and Their Implications in Predicting Graft Outcomes

Background: This study aimed to assess the association between the percentage of glomerulosclerosis (GS) in procurement allograft biopsies from high-risk deceased donor and graft outcomes in kidney transplant recipients. Methods: The UNOS database was used to identify deceased-donor kidneys with a kidney donor profile index (KDPI) score > 85% from 2005 to 2014. Deceased donor kidneys were categorized based on the percentage of GS: 0-10%, 11-20%, >20% and no biopsy performed. The outcome included death-censored graft survival, patient survival, rate of delayed graft function, and 1-year acute rejection. Results: Of 22,006 kidneys, 91.2% were biopsied showing 0-10% GS (58.0%), 11-20% GS (13.5%), >20% GS (19.7%); 8.8% were not biopsied. The rate of kidney discard was 48.5%; 33.6% in 0-10% GS, 68.9% in 11-20% GS, and 77.4% in >20% GS. 49.8% of kidneys were discarded in those that were not biopsied. Death-censored graft survival at 5 years was 75.8% for 0-10% GS, 70.9% for >10% GS, and 74.8% for the no biopsy group. Among kidneys with >10% GS, there was no significant difference in death-censored graft survival between 11-20% GS and >20% GS. Recipients with >10% GS had an increased risk of graft failure (HR = 1.27, p < 0.001), compared with 0-10% GS. There was no significant difference in patient survival, acute rejection at 1-year, and delayed graft function between 0% and 10% GS and >10% GS. Conclusion: In >85% KDPI kidneys, our study suggested that discard rates increased with higher percentages of GS, and GS >10% is an independent prognostic factor for graft failure. Due to organ shortage, future studies are needed to identify strategies to use these marginal kidneys safely and improve outcomes.

Can Behavioral Research Improve Transplant Decision-Making? A Mock Offer Study on the Role of Kidney Procurement Biopsies

Background

The use of procurement biopsies for assessing kidney quality has been implicated as a driver of the nearly 20% kidney discard rate in the United States. Yet in some contexts, biopsies may boost clinical confidence, enabling acceptance of kidneys that would otherwise be discarded. We leveraged a novel organ offer simulation platform to conduct a controlled experiment isolating biopsy effects on offer acceptance decisions.

Methods

Between November 26 and December 14, 2018, 41 kidney transplant surgeons and 27 transplant nephrologists each received the same 20 hypothetical kidney offers using a crossover design with weekend "washout" periods. Mini-study 1 included four, low serum creatinine (<1.5 mg/dl) donor offers with arguably "poor" biopsy findings that were based on real offers that were accepted with successful 3-year recipient outcome. For each of the four offers, two experimental variants-no biopsy and "good" biopsy-were also sent. Mini-study 2 included four AKI offers with no biopsy, each having an offer variant with "good" biopsy findings.

Results

Among low serum creatinine donor offers, we found approximately threefold higher odds of acceptance when arguably poor biopsy findings were hidden or replaced with good biopsy findings. Among AKI donor offers, we found nearly fourfold higher odds of acceptance with good biopsy findings compared with no biopsy. Biopsy information had profound but variable effects on decision making: more participants appeared to have been influenced by biopsies to rule out, versus rule in, transplantable kidneys.

Conclusions

The current use of biopsies in the United States appears skewed toward inducing kidney discard. Several areas for improvement, including reducing variation in offer acceptance decisions and more accurate interpretation of findings, have the potential to make better use of scarce, donated organs. Offer simulation studies are a viable research tool for understanding decision making and identifying ways to improve the transplant system.

Isolated pancreas transplantation: Is rank list position related to outcomes of imported grafts?

Transplant centers may decline an import pancreas offer based on demographics and laboratory test results, without information on actual gland quality. The relationship between position on the match run, indicative of the number of centers that chose not to use a pancreas, and patient and death-censored graft survival, is not known. We studied all 199 isolated pancreas grafts transplanted at the University of Wisconsin since July 2000 and compared overall patient and death-censored graft survival based on import vs local status. Of the 199 isolated pancreas transplants, 184 (92.5%) were imported from another donor service area with a median match rank of 49 (interquartile range 14-129). Median cold ischemia time was longer for imported pancreata (16.6 vs 13.4 hours, P = .02). In multivariate Cox modeling, there was no association with position on the rank list and patient (P = .44) or death-censored graft survival (P = .99). There was an overall rate of 6.5% of graft failure within 30 days; however, there was no association with position on the rank list and graft failure at 30 days (P = .33). Although the logistics may be challenging, sound judgment to accept offers independent of prior centers' decisions can result in quality utilization of imported pancreata.

Association Between Declined Offers of Deceased Donor Kidney Allograft and Outcomes in Kidney Transplant Candidates

IMPORTANCE

In the United States, substantial disparities in access to kidney transplant exist for wait-listed candidates with end-stage renal disease. The implications of transplant centers' willingness to accept kidney offers for access to transplant and mortality outcomes are unknown.

OBJECTIVE

To determine the outcomes for wait-listed kidney transplant candidates after the transplant center's refusal of a deceased donor kidney offer.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study obtained data from the United Network for Organ Sharing Potential Transplant Recipient data set on all deceased donor kidney offers in the United States made between January 1, 2008, and December 31, 2015. The final study cohort included adult patients who were wait-listed for kidney transplant and received at least 1 allograft offer during the study period (N = 280 041). Data analysis was conducted from June 1, 2018, to March 30, 2019.

EXPOSURE

Candidate state of residence.

MAIN OUTCOMES AND MEASURES

Waiting list outcome event groups included received deceased donor allograft, received living donor allograft, died while on the waiting list, removed from the waiting list without a transplant, or still on the waiting list at the end of follow-up.

RESULTS

Among the 280 041 kidney transplant candidates included in the study, the mean (SD) age at wait-listing was 51.1 (13.1) years, and male patients were predominant (171 517 [61.2%]). In this cohort, 81 750 candidates (29.2%) received a deceased donor kidney allograft, 30 870 (11.0%) received a living donor allograft, 25 967 (9.3%) died while on the waiting list, and 59 359 (21.2%) were removed from the waiting list. Overall, 10 candidates with at least 1 previous allograft offer died each day during the study period. Time to first offer was similar for candidates who received deceased donor kidney allograft compared with those who died while waiting (median [interquartile range {IQR}] time, 79 [16-426] days vs 78 [17-401] days, respectively). Deceased donor allograft recipients had a median of 17 offers (IQR, 6-44) over 422 days (IQR, 106-909 days), whereas candidates who died while waiting received a median of 16 offers (IQR, 6-41) over 651 days (IQR, 304-1117 days). Most kidneys (84%) were declined on behalf of at least 1 candidate before being accepted for transplant. As reported by centers, organ or donor quality concerns accounted for 8 416 474 (92.6%) of all declined offers, whereas offers were infrequently refused because of patient-related factors (232 193 [2.6%]), logistical limitations (49 492 [0.5%]), or other concerns. The odds of death after an offer and the median number of offers received prior to death varied considerably by state.

CONCLUSIONS AND RELEVANCE

This study found that transplant candidates appeared to receive a large number of viable deceased donor kidney offers that were refused on their behalf by transplant centers, potentially exacerbating the detrimental consequences of the organ shortage; increased transparency in organ allocation process and decisions may improve patient-centered care and access to kidney transplant.

Use of public health service increased risk kidneys in pediatric renal transplant recipients

With the opioid epidemic and expansion of "IR" classification, 25% of deceased donors are categorized PHS-IR. Studies have assessed utilization of PHS-IR organs among adults, but little is known about pediatric recipients. This retrospective cohort study from 2004-2016 (IR period) aimed to: (a) assess IR kidney utilization patterns between adults and children; (b) identify recipient factors associated with transplant from IR donors among pediatric kidney recipients; and (c) determine geography's role in IR kidney utilization for children. The proportion of pediatric recipients receiving IR kidneys was significantly lower than adults (P < 0.001), even when stratified by donor mechanism of death (non-overdose/overdose) and era. In mixed effects models accounting for clustering within centers and regions, older recipient age, later era (post-PHS-IR expansion), and blood type were associated with significantly higher odds of receiving an IR kidney (17 years era 5: OR 5.16 [CI 2.05-13.1] P < 0.001; 18-21 years era 5: OR 2.72 [CI 1.05-7.06] P = 0.04; blood type O: OR 1.32 [CI 1.06-1.64] P = 0.013). The median odds ratio for center within region was 1.77 indicating that when comparing two patients in a region, the odds of receiving an IR kidney were 77% higher for a patient from a center with higher likelihood of receiving an IR kidney. Utilization of PHS-IR kidneys is significantly lower among pediatric recipients versus adult counterparts. More work is needed to understand the reasons for these differences in children in order to continue their access to this life-prolonging therapy.

Leveraging marginal structural modeling with Cox regression to assess the survival benefit of accepting vs declining kidney allograft offers

Existing studies evaluating the survival benefit of kidney transplantation were unable to incorporate time-updated information on decisions related to each organ offer. We used national registry data, including organ turndown data, to evaluate the survival benefit of accepting vs turning down kidney offers in candidates waitlisted from 2007-2013. Among candidates who declined their first offer, only 43% ultimately received organ transplantations. Recipients who later underwent organ transplantation after declining their first offer had markedly longer wait times than recipients who accepted their first offer, and 56% received kidney transplants that were of similar or lower quality compared to their initial offer. In marginal structural modeling analyses accounting for time-updated offer characteristics (including Kidney Donor Profile Index, Public Health System risk status, and pumping), after 3 months posttransplant, there was a significant survival benefit of accepting an offer (adjusted hazard ratio 0.76, 95% confidence interval 0.66-0.89) that was similar among diabetics, candidates aged >65 years, and candidates living in donor service areas with the longest waitlist times. After carefully accounting for the effect of donor quality, we confirm that the survival benefit of accepting an organ offer is clinically meaningful and persistent beyond 3 months post-kidney transplantation, including high-risk subgroups of organ transplantation candidates.

Donor Lung Sequence Number and Survival after Lung Transplantation in the United States

RATIONALE

In the United States, an algorithm known as the "match-run" creates an ordered ranking of potential recipients for available lung allografts. A potential recipient's match-run position, or "sequence number," is available to the transplant center when contacted with a lung offer. Lung offers with higher sequence numbers may be interpreted as a crowd-sourced evaluation of poor organ quality, though the association between the sequence number at which a lung is accepted and its recipient's post-transplant outcomes is unclear.

OBJECTIVES

We sought to evaluate the primary reasons provided when a lung offer was refused by a transplant center, transplant center and donor/organ factors associated with a higher sequence number at acceptance, and the association of the sequence number at acceptance with post-transplant mortality and graft failure.

METHODS

Match-run outcomes for lung offers that occurred in the United States from May 2007 through June 2014 were merged with recipient follow-up data through December 2017. Associations between the sequence number at the time of acceptance and selected transplant center and donor characteristics were estimated using multivariable logistic and multinomial regression models. The associations between the final sequence number and recipient survival and graft survival were estimated using multivariable time-to-event models.

RESULTS

Of 10,981 lung offer acceptances, nearly 70% were accepted by one of the top 10 ranked candidates. Higher median annual center volume and potential indicators of organ quality (e.g., abnormal chest radiograph or bronchoscopy) were associated with a higher sequence number at acceptance. There was weak evidence for a small positive relationship between the sequence number at acceptance and both mortality and graft failure. For example, the unadjusted and adjusted hazard ratios for death associated with the log-sequence number at acceptance were 1.019 (95% confidence interval, 1.001-1.038) and 1.011 (95% confidence interval, 0.989-1.033), respectively. On the absolute scale, using the multivariable model, a 10-fold increase in the sequence number translated into a 0.8% absolute decline in the predicted 5-year survival.

CONCLUSIONS

Acceptance of a donor lung offer at a later point in the match-run was associated with measurable indicators of organ quality, but not with clinically meaningful differences in post-transplant mortality or graft failure.

Weekend effect: analysing temporal trends in solid organ donation

BACKGROUND

Research suggests patients treated over weekends experience poorer outcomes. Only one US-based study explored this weekend effect in organ donation, specifically the kidney discard rate. In Australia potential donors are referred to a donation service, and donation proceeds if family consent is granted and the donor is deemed medically suitable to donate. Organ procurement occurs when utilization is almost certain hence discard rates are much lower than in the USA. We aimed to characterize the effect of weekend referral on organ donation in Australia.

METHODS

We retrospectively reviewed all New South Wales Organ and Tissue Donation Service logs from 2010 to 2016. Our primary outcome was progression to organ procurement, and secondary outcomes were family consent and meeting medical suitability thresholds. We used logistic regression with random effects adjusting for clustering of referral hospitals.

RESULTS

Of 3496 potential donors referred for consideration, 694 (20%) progressed to organ procurement. There were fewer referrals on weekends (average 415 versus 588 for weekdays). However, donation rates were no lower for weekend compared to weekday referrals (adjusted OR 1.17; 95% CI 0.95, 1.44). Family consent (adjusted OR 1.20; 95% CI 1.00, 1.44) and medical suitability (adjusted OR 1.15; 95% CI 0.96, 1.38) were not lower for weekend compared to weekday referrals. Similar results were found for all sensitivity analyses conducted.

CONCLUSIONS

In Australia, the donation pathway operates consistently throughout the week, with donation no less likely to proceed on weekends and holidays. This finding contrasts with findings in the USA.

Hard-to-place kidney offers: Donor- and system-level predictors of discard

Understanding risk factors for deceased-donor kidney nontransplantation is important since discard rates remain high. We analyzed DonorNet^® data of consecutive deceased-donor nonmandatory share primary kidney-only offers to adult candidates at our center and beyond between July 1, 2015 and March 31, 2016 for donor- and system-level risk factors of discard, defined as nontransplantation at our or subsequent transplant centers. Exclusions were hepatitis C virus/hepatitis B virus core antibody status, blood type AB, and donor <1 year based on low candidate waitlist size. Of 456 individual kidney offers, from 296 donors, 73% were discarded. Most were national (93%) offers from Kidney Donor Profile Index 35-85% (n = 233) or >85% (n = 208) donors late in the allocation sequence with prior refusals logged for numerous candidates. On multivariate regression, factors significantly associated with discard were donor cerebrovascular accident (adjusted odds ratio [aOR]: 3.32), cancer transmission concern (aOR: 6.5), renal artery luminal compromise (aOR: 3.97), biopsy score ≥3 (aOR: 5.09), 2-hour pump resistive index >0.4 (aOR: 3.27), absence of pump (aOR: 2.58), nonspecific kidney abnormality (aOR: 2.76), increasing offer cold ischemia time category 11-15, 16-20, and >21 hours (aOR: 2.07, 2.33, 2.82), nighttime notification (aOR: 2.19), and neither kidney placed at time of offer (aOR: 2.74). Many traditional determinants of discard lack discriminatory value when granular factors are assessed. System-level factors also influence discard and warrant further study.

Inferior long-term allograft and patient outcomes among recipients of offspring living donor kidneys

While offspring-to-parent living donor kidney transplantations may represent an ideal donor-recipient combination to optimize long-term transplantation outcomes, the sex-specific long-term success of these transplantations remains unclear. We hypothesize that allograft and recipient survivals in offspring-to-parent living donor kidney transplantation differ between men and women due to donor-specific alloimmunization during pregnancy. We retrospectively analyzed long-term allograft and patient survival among men and women who received an offspring living donor kidney compared with those who received other haplotype-matched living donor kidneys. Based on multivariable Cox proportional hazards modeling of Organ Procurement and Transplantation Network data from 2001 to 2015, we found that both men and women who received offspring living donor kidneys had significantly increased mortality compared with recipients who received nonoffspring living donor kidneys. While male recipients of any living donor kidney had greater risk of mortality and allograft failure than female recipients, there was no significant difference in all-cause allograft failure or mortality in male versus female recipients of offspring living donor kidney transplantations. Our analysis demonstrated no significant interaction between recipient sex and donor offspring status. We conclude that nonoffspring living donors should be considered whenever feasible for both men and women with multiple donor options.

The weekend effect in liver transplantation

Background

The weekend effect describes a phenomenon whereby patients admitted to hospitals on weekends are at higher risk of complications compared to those admitted during weekdays. However, if a weekend effect exists in orthotopic liver transplantation (oLT).

Methods

We analyzed oLT between 2006 and 2016 and stratified patients into weekday (Monday to Friday) and weekend (Saturday, Sunday) groups. Primary outcome measures were one-year patient and graft survival.

Results

364 deceased donor livers were transplanted into 329 patients with 246 weekday (74.77%) and 83 weekend (25.23%) patients. Potential confounders (e.g. age, ischemia time, MELD score) were comparable. One-year patient and graft survival were similar. Frequencies of rejections, primary-non function or re-transplantation were not different. The day of transplantation was not associated with one-year patient and graft survival in multivariate analysis.

Conclusions

We provide the first data for the Eurotransplant region on oLT stratified for weekend and weekday procedures and our findings suggest there was no weekend effect on oLT. While we hypothesize that the absent weekend effect is due to standardized transplant procedures and specialized multidisciplinary transplant teams, our results are encouraging showing oLT is a safe and successful procedure, independent from the day of the week.

Turn down for what? Patient outcomes associated with declining increased infectious risk kidneys

Transplant candidates who accept a kidney labeled increased risk for disease transmission (IRD) accept a low risk of window period infection, yet those who decline must wait for another offer that might harbor other risks or never even come. To characterize survival benefit of accepting IRD kidneys, we used 2010-2014 Scientific Registry of Transplant Recipients data to identify 104 998 adult transplant candidates who were offered IRD kidneys that were eventually accepted by someone; the median (interquartile range) Kidney Donor Profile Index (KDPI) of these kidneys was 30 (16-49). We followed patients from the offer decision until death or end-of-study. After 5 years, only 31.0% of candidates who declined IRDs later received non-IRD deceased donor kidney transplants; the median KDPI of these non-IRD kidneys was 52, compared to 21 of the IRDs they had declined. After a brief risk period in the first 30 days following IRD acceptance (adjusted hazard ratio [aHR] accept vs decline: _1.22 2.06_3.49 , P = .008) (absolute mortality 0.8% vs. 0.4%), those who accepted IRDs were at 33% lower risk of death 1-6 months postdecision (aHR _0.50 0.67_0.90 , P = .006), and at 48% lower risk of death beyond 6 months postdecision (aHR _0.46 0.52_0.58 , P < .001). Accepting an IRD kidney was associated with substantial long-term survival benefit; providers should consider this benefit when counseling patients on IRD offer acceptance.