The Donor Risk Score: A Simpler Method to Grade Liver Allografts

Context: Growing need for liver transplantation has led to increased efforts to utilize allografts for transplantation from an expanding donor pool (“marginal” donor livers). Objective: To devise a simplified practical donor allograft scoring system based primarily on allograft survival following liver transplantation. Methods: The United Network of Organ Sharing (UNOS) provided de-identified patient-level data. This study included all liver transplant recipients who received allografts between between March 1, 2002 and December 31, 2012. Patients who received combined, multivisceral, or live donor transplants and those with no available follow-up data were excluded from this study. We therefore analyzed a total of 49,656 liver transplant recipients for this study. Kaplan-Meier analysis with log-rank test and Cox proportion hazards regression were used for time-to-event analysis. Univariate and multivariate analyses identified significant and independent risk factors. Results: In addition to cold ischemia time we identified nine donor risk factors as significant for graft failure: 1) donor age, 2) donor height, 3) CVA as cause of death, 4) donor renal insufficiency, 5) diabetes in the donor, 6) national sharing, 7) hepatitis C in the donor, 8) ABO incompatible transplants and 9) donation after cardiac death. The most significant of these were 1) donation after cardiac death (RR 1.6) and 2) donor age > 70 (RR 1.6). Our novel Donor Risk Score assigns points to each donor risk factor on the basis of severity and these are ultimately added to each other to derive the final DRS score (total points) for a given allograft. Extended criteria donor allografts are defined as an allograft with five or more risk points which represent the worst 20% of allografts. Conclusion: The novel Donor Risk Score (DRS) is a simplified and practical method to evaluate and grade liver allografts. The derived risk points are simply added to each other to assign a DRS to the donor which is simpler to use to predict donor liver function than the presently recommended Donor Risk Index (DRI) that employs a complex exponential function. The DRS that we propose is also more marginally more predictive of graft survival compared to the DRI (c-statistic 0.58 vs 0.57, p