KDPI/KDRI and donor-quality concepts

KDPI (Kidney Donor Profile Index) and KDRI (Kidney Donor Risk Index) are the standardized measures of deceased-donor kidney quality used in United States kidney allocation.[1][2] The KDRI is a relative-risk score, derived from donor characteristics, that estimates how quickly a transplanted kidney is likely to fail compared with a reference kidney; the KDPI re-expresses that score as a percentile from 0 to 100 percent, where a lower KDPI indicates a kidney expected to function longer (a 0-20 percent kidney is in the top fifth, a KDPI above 85 percent is among the highest-risk).[1][2] Together with a candidate-side longevity score, KDPI replaced the older binary Standard Criteria Donor / Expanded Criteria Donor classification when the current allocation system took effect in 2014.[2][3]

KDPI is a population-relative index: a donor's KDRI is mapped against the distribution of KDRI values for all deceased donors recovered in a recent reference year, so the percentiles are recalibrated annually.[1] It is a probabilistic estimate of graft longevity, not a pass/fail verdict on a particular organ, and is one input among many in a transplant team's acceptance decision.[1]

What KDRI and KDPI are

The KDRI is computed from a Cox proportional-hazards model of deceased-donor graft failure: each donor variable carries a coefficient, and the model yields a relative risk normalized so that a "median" donor has a KDRI of about 1.0.[1][2] The KDPI then converts that continuous KDRI into an easily communicated percentile against the prior year's deceased-donor pool, for example, a KDPI of 30 percent means the kidney's KDRI is higher (worse) than 30 percent and lower (better) than 70 percent of last year's recovered kidneys.[1] The OPTN publishes an annually updated mapping table and calculator for clinicians.[1]

The donor variables

As originally implemented in 2014, the KDRI used about ten donor factors. After the 2024 refit (below), the calculation uses eight:[1][4]

| Variable | Notes | |---|---| | Age | Strongest single contributor; risk rises at the extremes | | Height | Entered in cm | | Weight | Entered in kg | | History of hypertension | Yes/no | | History of diabetes | Yes/no | | Cause of death | Cerebrovascular accident (stroke) carries added risk | | Serum creatinine | Marker of donor kidney function | | Donation after circulatory death (DCD) status | See deceased donation | | ~~Donor race/ethnicity (Black)~~ | Removed October 2024 | | ~~Hepatitis C virus (HCV) status~~ | Removed October 2024 |

Donor infection status, including HCV, is part of the broader donor evaluation and infectious-disease testing workup even though HCV serostatus no longer enters the KDRI formula.[4]

How KDPI is used in allocation

KDPI is central to the longevity-matching design of the Kidney Allocation System (KAS) implemented in December 2014.[2][3] On the candidate side, an Estimated Post-Transplant Survival (EPTS) score ranks candidates by expected post-transplant survival using age, time on dialysis, prior solid-organ transplant, and diabetes status. The system then preferentially offers the longest-expected-functioning kidneys (KDPI ≤ 20 percent) to candidates with the best expected survival (top 20 percent EPTS) before others, the so-called 20/20 longevity match, to align graft and recipient lifespans and reduce wasted graft years.[2][3] Kidneys with KDPI > 85 percent are higher-risk organs offered through a broader, expedited distribution to widen acceptance; programs are expected to obtain specific informed consent from candidates willing to accept them.[2][3]

History: what it replaced

Before 2014, deceased-donor kidneys were sorted into two categories: Standard Criteria Donor (SCD) and Expanded Criteria Donor (ECD), the latter defined by donor age ≥ 60, or age 50-59 with at least two of hypertension, cerebrovascular cause of death, or elevated creatinine.[2] The ECD label was a blunt binary cutoff that grouped very different kidneys together and gave little gradation. A KDPI of roughly 85 percent corresponds approximately to the old ECD threshold, and the move to a continuous 0-100 percent index was intended to give a finer, more informative measure of expected graft longevity while retiring the SCD/ECD terminology.[2][3]

Related concepts

The candidate-side analogue of KDPI is the EPTS score, which estimates how long a candidate is likely to benefit from a transplant.[2] Other organs use their own donor-quality or severity indices, for example, the Lung Allocation Score and Composite Allocation Score frameworks and various donor-risk indices for liver, though these are constructed differently and are not interchangeable with KDPI.[2]

Limitations and debate

KDPI has drawn sustained discussion on several points:[2][4][5]

• Discard of high-KDPI kidneys. Centers are reluctant to use kidneys labeled with high KDPI, contributing to discard of organs that might still benefit certain candidates; commentators warn the percentile label can be self-reinforcing.
• Calibration and recalibration. Because KDPI is mapped to a shifting reference population and was originally fitted on older cohorts, its calibration drifts over time, prompting periodic re-fitting.
• Race and HCV variables. The original KDRI included a coefficient that raised the risk score for Black donors and one for HCV-seropositive donors. Following evidence that direct-acting antiviral therapy had sharply reduced the risk of HCV-positive kidneys, and concern that the race coefficient inflated KDPI for kidneys from Black donors and worsened equity, the OPTN Minority Affairs Committee requested a refit. The OPTN Board of Directors approved removing both variables on June 17, 2024, and the refitted KDRI/KDPI, fitted on 2018-2021 transplants and using eight variables, was implemented in October 2024.[4][5][6] In the refit, the Black-race coefficient had only modestly decreased over time while the HCV coefficient had effectively vanished, and removing both did not materially harm the model's discrimination or calibration.[5] As of June 2026, the race- and HCV-free KDRI/KDPI is the operative formula in U.S. allocation.[4][6]

See also

• Kidney transplantation
• OPTN allocation policy
• Deceased donation
• Donor evaluation and infectious-disease testing
• Kidney paired donation / exchange

References

• Health Resources and Services Administration / OPTN. A Guide to Calculating and Interpreting the Kidney Donor Profile Index (KDPI). https://www.hrsa.gov/sites/default/files/hrsa/optn/kdpi_guide.pdf
• Israni AK, Salkowski N, Gustafson S, et al. New national allocation policy for deceased donor kidneys in the United States and possible effect on patient outcomes. J Am Soc Nephrol. 2014;25(8):1842-1848. doi:10.1681/ASN.2013070784. PMID:24833128. https://pmc.ncbi.nlm.nih.gov/articles/PMC4116061/
• Health Resources and Services Administration. Kidney Allocation System (KAS). (Implemented December 2014; longevity matching; KDPI ≤ 20% to top-20% EPTS; KDPI > 85% informed consent.) https://www.hrsa.gov/optn/professionals/resources/kidney-pancreas/kidney-allocation-system
• HRSA/OPTN. Six-month monitoring shows expected progress after KDPI policy change. (October 2024 implementation of refitted KDPI without race and HCV; eight variables.) https://www.hrsa.gov/optn/news-events/news/kdpi-policy-change
• Miller JM, Poff K, Howell JN, et al. Updating the kidney donor risk index: removing donor race and hepatitis C virus status. Am J Transplant. 2025;25(6):1285-1295. doi:10.1016/j.ajt.2025.01.015. https://www.amjtransplant.org/article/S1600-6135(25)00021-8/fulltext
• OPTN. Refit Kidney Donor Profile Index without Race and Hepatitis C Virus (policy approved by OPTN Board June 17, 2024). https://optn.transplant.hrsa.gov/policies-bylaws/public-comment/refit-kidney-donor-profile-index-without-race-and-hepatitis-c-virus/