Predicting patient survival after deceased donor kidney transplantation using flexible parametric modelling

BACKGROUND: The influence of donor and recipient factors on outcomes following kidney transplantation is commonly analysed using Cox regression models, but this approach is not useful for predicting long-term survival beyond observed data. We demonstrate the application of a flexible parametric approach to fit a model that can be extrapolated for the purpose of predicting mean patient survival. The primary motivation for this analysis is to develop a predictive model to estimate post-transplant survival based on individual patient characteristics to inform the design of alternative approaches to allocating deceased donor kidneys to those on the transplant waiting list in the United Kingdom. METHODS: We analysed data from over 12,000 recipients of deceased donor kidney or combined kidney and pancreas transplants between 2003 and 2012. We fitted a flexible parametric model incorporating restricted cubic splines to characterise the baseline hazard function and explored a range of covariates including recipient, donor and transplant-related factors. RESULTS: Multivariable analysis showed the risk of death increased with recipient and donor age, diabetic nephropathy as the recipient's primary renal diagnosis and donor hypertension. The risk of death was lower in female recipients, patients with polycystic kidney disease and recipients of pre-emptive transplants. The final model was used to extrapolate survival curves in order to calculate mean survival times for patients with specific characteristics. CONCLUSION: The use of flexible parametric modelling techniques allowed us to address some of the limitations of both the Cox regression approach and of standard parametric models when the goal is to predict long-term survival

Pancreas transplantation from donors after circulatory death from the United Kingdom.

This study reports the comparative short-term results of pancreas transplantation from donors after circulatory death (DCD) (Maastricht III and IV), and pancreases from brainstem deceased donors (DBD). Between January 2006 and December 2010, 1009 pancreas transplants were performed in the United Kingdom, with 134 grafts from DCD and 875 from DBD. DCD grafts had no premortem pharmacological interventions performed. One-year pancreas and patient survival was similar between DCD and DBD, with pancreas graft survival significantly better in the DCD cohort if performed as an SPK. Early graft loss due to thrombosis (8% vs. 4%) was mainly responsible for early graft loss in the DCD cohort. These results from donors with broader acceptance criteria in age, body mass index, premortem interventions, etc. suggest that DCD pancreas grafts may have a larger application potential than previously recognized

The deceased donor score system in kidney transplants from deceased donors after cardiac death.

SUMMARY: A clinical score to identify kidneys from donors after cardiac death (DCD) with a high risk of dysfunction following transplantation could be a useful tool to guide the introduction of new algorithms for the preservation of these organs and improve their outcome after transplantation. We investigated whether the deceased donor score (DDS) system could identify DCD kidneys with higher risk of early post-transplant dysfunction. The DDS was validated in a cohort of 168 kidney transplants from donors after brain death (DBD) and then applied to a cohort of 56 kidney transplants from DCD. In the DBD cohort, the DDS grade predicted the incidence of delayed graft function (DGF) and levels of serum creatinine at 3 and 12 months post-transplant. Similarly, in the DCD cohort, the DDS grade correlated with DGF and also predicted the levels of serum creatinine at 3 and 12 months. Interestingly, the DDS identified a subgroup of marginal DCD kidneys in which minimization of cold ischemia time produced better early clinical outcome. These results highlight the impact of early interventions on clinical outcome of marginal DCD kidneys and open the possibility of using the DDS to identify those kidneys that may benefit most from therapeutic interventions before transplantation

Expression of MHC class I-related Chain B (MICB) molecules on renal transplant biopsies.

BACKGROUND: MICA and MICB (MHC class I-related chain A and B) are polymorphic genes that encode molecules related to MHC class I and are expressed on epithelial cells in response to stress. Incompatible donor MIC antigens can stimulate antibody production in transplant recipients. This study was designed to determine MICB expression in kidney pretransplant and any subsequent changes in expression following transplantation and to correlate changes with inflammatory markers and clinical events. METHODS: Paired renal biopsies obtained from living donor (n=10) and cadaveric allografts (n=50) before and 7 days posttransplant were stained for MICB, leukocytic infiltration, and HLA class II antigens. RESULTS: Variable tubular MICB expression was evident in donor biopsies [high 6/60 (10%), low/negative 13/60 (22%), intermediate 41/60 (68%)]. Following transplantation, MICB was up-regulated on renal tubules of 17/60 (28%) biopsies and was associated with MHC class II antigen induction (P=0.02) and leukocyte infiltration (P=0.01). Acute tubular necrosis leading to delayed graft function (DGF) and acute rejection (AR) cause cellular stress within the transplanted kidney. We found a strong association between up-regulation of MICB and cellular stress, 15/17 biopsies with up-regulated MICB expression had AR and/or DGF (P=0.003). CONCLUSIONS: This is the first study demonstrating variable levels of MICB expression in kidneys before transplantation and induction of MICB expression following renal transplantation. MICB expression is associated with HLA class II antigen induction, leukocytic infiltration of the graft and cellular stress in the transplanted kidney. Expression of MICB could contribute significantly to the alloimmune response in mismatched donors and recipients

Endothelial cell protection against ischemia/reperfusion injury by lecithinized superoxide dismutase.

BACKGROUND: Organs used for transplantation may experience long periods of cold ischemic preservation and consequently oxygen free radical-mediated damage following reperfusion. Lecithinized superoxide dismutase (lec-SOD) is a novel free radical scavenger that has been shown to bind with high affinity to cell membranes. The aim of this study was to determine whether lec-SOD bound to endothelial cells under organ preservation conditions to mediate direct antioxidant activity at the endothelial cell surface and thus offer protection against the harmful effects of ischemia/reperfusion injury. METHODS: An in vitro study was performed on large vessel endothelial cells (HUVEC) and a human microvascular endothelial cell line HMEC-1, to investigate the potential therapeutic benefits of incorporating lec-SOD into organ preservation solution. A cold hypoxia/reoxygenation system was developed to examine lec-SOD binding affinity to endothelial cells, protection against hypoxia/reoxygenation-induced cell death, and neutrophil adhesion. RESULTS: Lec-SOD bound to endothelial cells with higher affinity than unmodified recombinant human superoxide dismutase (rhSOD) and significantly protected both HUVEC and HMEC-1 from cell death following 27 hours of cold hypoxia (P < 0.01). Furthermore, neutrophil adhesion to the endothelium stimulated by hypoxia and reoxygenation was significantly inhibited by treatment with lec-SOD but not by lecithin or rhSOD (P < 0.01). Analysis by flow cytometry demonstrated that E-selectin and ICAM-1 were up-regulated by hypoxia/reoxygenation that was inhibited in part by lec-SOD. CONCLUSIONS: The results from this study suggest that incorporation of lec-SOD into organ preservation solutions provides effective protection to endothelial cells against cold ischemia and reperfusion injury following transplantation