Is the kidney donor profile index (KDPI) universal or UNOS-specific?

To the Editor: With the introduction of the Kidney Donor Profile Index (KDPI) scoring system in June 2013, allocation of kidney allografts and predicted outcomes in the United Network for Organ Sharing (UNOS) have changed. Although the hope was to reduce the discard rate of “marginal” or “extended criteria donor (ECD)” kidneys allocating them in a better way, the discard rate did not differ compared to the ECD era.1Bae S Massie AB Luo X Anjum S Desai NM Segev DL Changes in discard rate after the introduction of the kidney donor profile index (KDPI).Am J Transplant. 2016; 16: 2202-2207Abstract Full Text Full Text PDF PubMed Scopus (108) Google Scholar The transplantation community continues to seek ways to improve kidney allocation in order to provide acceptable (or even better) outcomes using the most possible deceased donor kidneys reducing the discard rate. One way to boost the use of higher-risk kidneys is allocating them as dual kidney transplantation (DKT).2Tanriover B Mohan S Cohen SJ et al.Kidneys at higher risk of discard: expanding the role of dual kidney transplantation.Am J Transplant. 2014; 14: 404-415Abstract Full Text Full Text PDF PubMed Scopus (96) Google Scholar DKT could provide increased nephron mass and therefore better expected outcomes compared to single use of ECD kidneys. However, transplant physicians seek to improve allocation of ECD kidneys as two single kidneys instead of DKT in order to expand the donor pool.3Gandolfini I Buzio C Zanelli P et al.The kidney donor profile index (KDPI) of marginal donors allocated by standardized pretransplant donor biopsy assessment: distribution and association with graft outcomes.Am J Transplant. 2014; 14: 2515-2525Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar Most recently, a multicenter controlled study showed that kidneys procured from donors >80 years old could be allocated as single or DKT after a pre-transplant biopsy assessment despite their calculated KDPI scores (96-100%). The study provided comparable outcomes as single standard criteria kidney transplantation up to 7 years with the use of kidneys which had KDPI >96%.4Ruggenenti P, Silvestre C, Boschiero L, et al. Long-term outcome of renal transplantation from octogenarian donors: a multicenter controlled study [published online ahead of print 2017]. Am J Transplant. https://doi.org/10.1111/ajt.14459.Google Scholar Those kidneys may have been discarded by a UNOS center based on their KDPI scores.1Bae S Massie AB Luo X Anjum S Desai NM Segev DL Changes in discard rate after the introduction of the kidney donor profile index (KDPI).Am J Transplant. 2016; 16: 2202-2207Abstract Full Text Full Text PDF PubMed Scopus (108) Google Scholar The recent publication by Ruggenenti et al4Ruggenenti P, Silvestre C, Boschiero L, et al. Long-term outcome of renal transplantation from octogenarian donors: a multicenter controlled study [published online ahead of print 2017]. Am J Transplant. https://doi.org/10.1111/ajt.14459.Google Scholar prompted us to look back at a publication by Ekser et al5Ekser B Furian L Broggiato A et al.Technical aspects of unilateral dual kidney transplantation from expanded criteria donors: experience of 100 patients.Am J Transplant. 2010; 10: 2000-2007Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar in 2010 and calculate the KDPI of 100 ECD donors with a mean age of 72, transplanted as DKT. The calculated KDPI scores using the online calculator (Figure 1) was 96.9 ± 3.4%.5Ekser B Furian L Broggiato A et al.Technical aspects of unilateral dual kidney transplantation from expanded criteria donors: experience of 100 patients.Am J Transplant. 2010; 10: 2000-2007Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar Fifty-six percent of donors had a KDPI of ≥98%. Only four (4%) patients had a KDPI of 90% or less (Figure 1). Based on the KDPI calculation from Ekser et al’s publication,5Ekser B Furian L Broggiato A et al.Technical aspects of unilateral dual kidney transplantation from expanded criteria donors: experience of 100 patients.Am J Transplant. 2010; 10: 2000-2007Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar >80% of those kidneys may have been discarded by a UNOS center. However, 5-year graft survival was recorded 91% using 100 ECD kidneys with a mean KDPI score of 97% (Figure 1).5Ekser B Furian L Broggiato A et al.Technical aspects of unilateral dual kidney transplantation from expanded criteria donors: experience of 100 patients.Am J Transplant. 2010; 10: 2000-2007Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar With more data becoming available on the use of ECD kidneys with KDPI scores >90% with comparable outcomes to single standard kidney transplantation, we wonder whether the kidney allocation based on the KDPI score and predicted outcomes is optimal for both organ utilization and recipient outcomes. Another approach could be performing pre-transplant kidney biopsies on higher KDPI kidneys (>90%) and allocate them based on the biopsy score (which should be read by a renal expert pathologist, though this could be challenging in many areas) rather than the KDPI score. Randomized studies using both criteria will be helpful to understand the real value of the KDPI score in higher risk kidneys (ie, KDPI of >90%) and would answer the question whether the KDPI is universal or UNOS-specific, keeping in mind that recipient factors may be as important as donor factors. We believe that the impact of pre-transplant kidney biopsies on higher KDPI scores would only be positive expanding the donor pool and providing better outcomes. The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation.