Association between Kidney Donor Risk Index, kidney graft function and histological changes in early post-transplant graft biopsy

Background

Proper assessment of donor organ quality is crucial for optimal kidney allocation and best long-term outcomes. The aim of this study was to analyze the association between the Kidney Donor Risk Index (KDRI) and histological parameters in early post-transplant graft biopsy in a Polish cohort of kidney transplant recipients.

Methods

In 418 consecutive kidney transplant recipients, a histological evaluation of very early [at median 11 (9-13) post-transplant day] protocol core needle biopsy was performed and analyzed according to the Banff classification. Subjects were divided into quartiles of the KDRI value. Kidney graft function, patient and graft survival were also analyzed over a median follow-up period of 44 (26-56) months.

Results

There was a significant trend toward greater intensity of chronic histology changes along the KDRI quartiles (χ2 = 20.8; P < .001), including interstitial fibrosis, tubular atrophy, mesangial matrix increase and arteriolar hyalinosis. Stepwise multivariate regression analysis revealed that only higher KDRI value independently increased the severity of chronic graft injury (rpartial = 0.340, P < .001). KDRI values were valuable in the determination of both early and long-term graft function.

Conclusion

The KDRI values correlate with chronic histological changes found in early post-implantation kidney biopsies and can also be helpful in the prediction of graft outcome.

Covariates adjustment questioned conclusions of predictive analyses: an illustration with the Kidney Donor Risk Index

OBJECTIVES

We aimed to illustrate that considering covariates can lead to meaningful interpretation of the discriminative capacities of a prognostic marker. For this, we evaluated the ability of the Kidney Donor Risk Index (KDRI) to discriminate kidney graft failure risk.

STUDY DESIGN AND SETTING

From 4114 French patients, we estimated the adjusted area under the time-dependent ROC curve by standardizing the marker and weighting the observations. By weighting the contributions, we also studied the impact of KDRI-based transplantations on the patient and graft survival.

RESULTS

The covariate-adjusted AUC varied from 55% (95% confidence interval [CI]: 51-60%) for a prognostic up to 1 year post-transplantation to 56% (95% CI: 52-59%) up to 7 years. The Restricted Mean Survival Time (RMST) was 6.44 years for high-quality graft recipients (95% CI: 6.30-6.56) and would have been 6.31 years (95% CI: 6.13-6.46) if they had medium-quality transplants. The RMST was 5.10 years for low-quality graft recipients (95% CI: 4.90-5.31) and would have been 5.52 years (95% CI: 5.17-5.83) if they had medium-quality transplants.

CONCLUSION

We demonstrated that the KDRI discriminative capacities were mainly explained by the recipient characteristics. We also showed that counterfactual estimations, often used in causal studies, are also interesting in predictive studies, especially regarding the new available methods.

Predicting Clinical Outcome in Expanded Criteria Donor Kidney Transplantation: A Retrospective Cohort Study

Background:

The gaps in organ supply and demand necessitate the use of expanded criteria donor (ECD) kidneys.

Objective:

To identify which pre-transplant and post-transplant predictors are most informative regarding short- and long-term ECD transplant outcomes.

Design:

Retrospective cohort study.

Setting:

Single center, Quebec, Canada.

Patients:

The patients were 163 consecutive first-time ECD kidney only transplant recipients who underwent transplantation at McGill University Health Centre (MUHC) between January 1, 2008 and December 31, 2014 and had frozen section wedge procurement biopsies.

Measurements:

Short-term graft outcomes, including delayed graft function and 1-year estimated glomerular filtration rate (eGFR), as well as long-term outcomes including all-cause graft loss (defined as return to dialysis, retransplantation, and death with function).

Methods:

Pre-transplant donor, recipient, and transplant characteristics were assessed as predictors of transplant outcomes. The added value of post-transplant predictors, including longitudinal eGFR, was also assessed using time-varying Cox proportional hazards models.

Results:

In univariate analyses, among the pre-transplant donor characteristics, histopathologic variables did not show evidence of association with delayed graft function, 1-year post-transplant eGFR or all cause graft loss. Recipient age was associated with all-cause graft loss (hazard ratio: 1.038 [95% confidence interval: 1.002-1.075] and the model produced only modest discrimination (C-index: 0.590; standard error [SE]: 0.045). Inclusion of time-dependent post-transplant eGFR improved the model’s prediction accuracy (C-index: 0.711; SE = 0.047). Pre-transplant ECD characteristics were not associated with long-term survival, whereas post-transplant characteristics allowed better model discrimination.

Limitations:

Single-center study, small sample size, and potential incomplete capture of all covariate data.

Conclusions:

Incorporation of dynamic prediction models into electronic health records may enable timely mitigation of ECD graft failure risk and/or facilitate planning for renal replacement therapies. Histopathologic findings on preimplantation biopsies have a limited role in predicting long-term ECD outcomes.

Trial registration:

Not applicable.

A Clinical Study on Cadaveric Kidney Donors in Puerto Rico and the Survival outcome of the grafts: a retrospective study of 187 kidneys from 2009-2011

OBJECTIVE

In this study, we assessed the Kidney Donor Risk Index (KDRI) in Puerto Rican deceased kidney donors whose donations took place from 2009 to 2011 and evaluated short-term graft survival in the recipients of those kidneys. The results highlight differences between the distributions of KDRI values in the populations of the 48 contiguous states of the United States, Alaska, and Hawaii and that of Puerto Rico. Additionally, we evaluated the impacts of polyomavirus (BKV) infection and anti-donor HLA antibodies on the recipients.

METHODS

Of the 377 kidneys obtained from deceased donors by LifeLink of Puerto Rico from 2009 to 2011, 187 were transplanted in Puerto Rico. Data was collected from the deceased donors of these 187 kidneys for calculating KDRI, as well as from the transplant recipients. KDRI values of the donors were calculated using the same formula as previously reported for the United States; death-censored graft survival, incidence of antibody-mediated rejection, and prevalence of polyoma virus infection (BKV) were examined in the recipients.

RESULTS

The mean KDRI value was 1.19. However, the distribution of KDRI values in the Puerto Rican population deviates substantially from that of the United States (not including Puerto Rico). A 1-peak distribution pattern describes Puerto Rican KDRI values. Graft survival for the study period was 89.6%. The prevalence of BKV was 16.9%. Of the patients studied, 6.25% developed overt nephropathy, 46.2% developed de novo post-transplant donor-specific alloantibodies, and 19.5% had pre-existing alloantibodies.

CONCLUSION

Our study evidences the role of various characteristics in the distribution of KDRI values in the Puerto Rican population, suggesting that the identification of variables specific to a geographically distinct group may result in better donor categorization for predicting transplant outcomes. In addition, our graft-survival results, despite the elevated rates of BKV and anti-donor antibodies, highlight the increasing need to monitor the presence of antibodies in a prospective and an anticipatory manner to identify and manage patients at risk for antibodymediated rejection.

R Open Source Programming Code for Calculation of the Kidney Donor Profile Index and Kidney Donor Risk Index

BACKGROUND

The Kidney Donor Profile Index (KDPI) and Kidney Donor Risk Index (KDRI) were developed by the United States Organ Procurement and Transplantation Network (OPTN). They may influence the clinical decision whether to accept or discard a donor kidney, but still there are debates about KDPI/KDRI applicability and its consequences. To further evaluate these indexes in different populations, more data should be analyzed, and a universally applicable program code would facilitate it. Currently, KDPI/KDRI calculation could be readily done only on the OPTN website that is convenient for a single donor, but not suitable for processing data sets with many records.

SUMMARY

A universally applicable program algorithm in widely used R language for calculating KDPI and KDRI was developed according to donor factors and coefficients described in the OPTN guide.

KEY MESSAGES

The open R code permits to calculate KDPI/KDRI either for a single donor or for an unlimited number of records in large data sets. The presented software code would save substantial time to research groups all over the world and help to clarify the KDPI/KDRI role in global settings.

Is the Kidney Donor Risk Index a Useful Tool in Non-US Patients?

Background:

Deceased donor kidney allocation in the United States is guided by the Kidney Donor Risk Index (KDRI). The generalizability of the KDRI beyond the United States has not been widely studied.

Objective:

To assess the generalizability of the KDRI in a cohort of non-US (Canadian) deceased donor kidney transplant recipients.

Design:

Population-based retrospective cohort study.

Setting:

Ontario, Canada.

Patients:

Recipients of deceased donor kidneys from January 1, 2005, to March 31, 2011.

Methods:

Using administrative data, we analyzed a cohort of deceased donor kidney recipients in Ontario, Canada. The Kaplan-Meier method and Cox proportional hazards models were used to assess the relationship between KDRI and the outcomes of graft loss and death. KDRI was modeled continuously and categorically. The ability of models with KDRI to predict recipient outcomes beyond donor age was also explored. Model discrimination was assessed using c-statistics, evaluated at 5 years of follow-up.

Results:

A total of 1299 consecutive deceased donor kidney transplant recipients were included. The median follow-up was 5.5 years. Mean donor age increased from 27 to 64 years across ascending KDRI quintiles. The adjusted relative hazards (95% confidence interval) for total graft loss from Q2 to Q5 (referent = Q1) were 1.27 (0.89-1.80), 1.58 (1.13-2.22), 1.43 (1.01-2.02), and 2.15 (1.54-2.99), respectively. Increased relative hazards across KDRI quintiles were also observed for death-censored graft loss, but not death with graft function. All-cause mortality was increased for the highest KDRI quintile only. In this cohort, a model with KDRI performed better than a model with donor age alone (P = .009).

Limitations:

Large health care databases may have precluded the complete capture of covariate data.

Conclusions:

In conclusion, the KDRI is generalizable to Canadian patients in Ontario and may help inform risk assessment beyond donor age. The performance of KDRI in other non-US settings, and the need for additional model refinement, warrants further study.

An Examination of the Application of the Kidney Donor Risk Index in British Columbia

Background:

The Kidney Donor Risk Index (KDRI) is a continuous measure of deceased donor kidney transplant failure risk that was derived in US patients based on 10 donor characteristics. In the United States, the KDRI is utilized to guide organ allocation and to inform clinical decisions regarding organ acceptance.

Objective:

To examine the application of the US-derived KDRI in a large Canadian province.

Patients:

All deceased donor kidney-only transplant recipients in British Columbia (BC) between 2005 and 2014.

Methods:

We examined the predictive performance of KDRI in BC transplant recipients and compared the overall performance of KDRI with donor age alone in predicting transplant failure (from all causes including death).

Results:

Donors in BC (N = 785) were older but included no black donors and few Hepatitis C virus (HCV)-positive donors compared with the original derivation cohort of the KDRI in the United States. The KDRI was moderately predictive of transplant failure (c statistic, 0.63) and had similar predictive performance to donor age alone (c statistic, 0.64).

Conclusion:

Our findings suggest that the US-derived KDRI does not improve the prediction of kidney transplant failure compared with donor age alone in a Canadian cohort and highlight the need to determine the applicability of KDRI in different regions.