Incorporation of Donor Risk Into Liver Allocation Algorithms

Abstract

WewouldliketothankAvolioetal.(1)forthecommentsonour article on the Eurotransplant Donor Risk Index (ET-DRI)(2). The Authors address an important issue: the practicalincorporation of donor risk into liver allocation algorithms.ItissuggestedthattheET-DRIshouldfirstbecomparedtoexisting donor-to-recipient-matching (D2Rm)-models, suchas D-MELD (3), BAR (4) or SOFT (5), for applicability andaccuracy before using it in liver allocation.We fully agree that transplantation outcome depends ondonor,transplantandrecipientriskfactors.Ofcourse,com-bining all these factors would lead to the best assess-ment of pretransplant risk and therefore best estimationof posttransplant results (note that all risk models arefrom observational studies, and have never been testedprospectively to confirm predictive value). The first stepis to look into donor and transplant factors, as did Fenget al. (6) for the UNOS region. In our current study wedescribe all significant donor- and transplant risk factorswithin the Eurotransplant-region, and combine these intoone number/score—the ET-DRI. The scores mentioned byAvolio et al. only include some of these factors or fac-tors that were not significant in our study; D-MELD onlyincludes donor age, BAR includes donor age and cold is-chemia time (CIT), and SOFT includes donor age, cause ofdeath, creatinine, allocation and CIT. The interesting thingabout the ET-DRI (and DRI) is that it is the strongest risk in-dicator when looking at donor and transplant factors, and itisacontinuousandvalidatedscore.Itprovidesonenumberthat represents the hazard ratio (HR) of that specific liverallograft, including the transplant factors allocation and CIT.Step 2 will be to investigate significant risk factor in recip-ients. Ultimately, research will be needed to see how tobest integrate both (donor/transplant and recipient) scoresto develop a D2R model, as stated by Avolio et al.Scores like D-MELD, BAR and SOFT do not take thestrongest donor factors into account: split-liver (HR1.67)and donation after cardiac death (DCD) (HR1.71). Althoughsuch allografts are scarce for the total Eurotransplant re-gion (6.5%), they account for almost 25% in, for example,the Netherlands, and in our opinion should therefore beincorporated in donor risk stratification.Clearly, further research is needed, especially for recipientrisk factors. The ET-DRI (DRI) gives a validated specific HRfor every single allograft, which is necessary to correct forinsuchresearch.Currentlytheonlyfactorusedinallocationistheextendedcriteriadonor(ECD).Weshowedthesupe-riorityofET-DRIoverECDforusewithintheEurotransplantregion.Furtherstepstobetakenaredevelopmentofa(val-idated) recipient risk index and the incorporation of donorand recipient risk scores into a risk stratifying model.Finally we agree that scores may be helpful for alloca-tion, but cannot replace individual assessment and deci-sion making of the transplantation team. In addition, thesocioethical choice of weighting utility versus equity re-mains a major factor of impact of how allocation will besteered in different countries. ET-DRI is a tool, rather thana means, which can be used to do this.