Prolonged Preservation Time Obviates the Benefits of 0 HLA Mismatches in Renal Transplantation

As long as the demand for transplantable organs exceeds the supply, fair and equitable organ allocation policies will be of utmost importance. However, these policies are often contentious and must balance a variety of disparate interests. Current kidney allocation policies in the United States have resulted in profound variations in waiting times for patients on the cadaveric renal transplant waiting list. For example, tenfold differences in average waiting times exist for patients of the O blood group based on their geographic location. The policy of national sharing of 0 HLA mismatched kidneys may contribute to some degree of equity in kidney allocation by evening the playing field for patients in all geographic locations. However, this policy is not universally embraced. Thus, Lee and colleagues should be congratulated for their critical analysis of this policy in their article.¹

I would like to offer an alternative hypothesis to explain the observation that 0 HLA mismatched kidneys with more than 36 hours of cold ischemic time had comparable allograft survival rates with inferiorly matched kidneys with less ischemic time. Rather than worsening allograft function and survival, prolonged ischemia times may indicate a suboptimal donor kidney. Most kidneys that are shared because of the 0 HLA mismatch policy have relatively common HLA haplotypes. Frequently, there are multiple potential 0 mismatch recipients throughout the country. It has been my experience that with ideal donor kidneys, the disposition is achieved rapidly, and ischemic time is minimized. However, kidneys from less-than-optimal donors are frequently refused and are offered to multiple centers despite excellent HLA matching. This "shopping around" for an accepting center contributes to prolonged cold ischemic times. Not uncommonly, suboptimal kidneys are accepted for transplantation solely because of the advantage of the high degree of HLA matching, which abrogates their poor qualities.

Multivariate analysis of factors that contribute to cadaveric kidney quality, such as donor age, terminal creatinine, hemodynamic instability, comorbid conditions (eg, hypertension or diabetes), and anatomic anomalies, must be performed to either prove or refute this hypothesis. Until this analysis is done, it would be premature to assume that national sharing of 0 HLA mismatched kidneys and the associated prolonged ischemic times are deleterious. Rather, this policy may provide the most efficacious use of these kidneys despite extending ischemic times.