A Validated Model for Predicting Outcome after Liver Transplantation: Implications on Transplanting the Extremely Sick (2012)

Introduction: The transplantation community is facing an ongoing crisis of organ shortage. In a “sickest first” allocation system, some patients are transplanted at the extreme of their disease. Few of them achieve very poor results. We sought to identify risk factors associated with inferior results and develop a model for predicting such outcome, in an intention to minimize sub-optimal outcome and loss of scarce organs. Methods: The study is a retrospective cohort analysis, based on a single institution prospectively maintained database. Hospital length of stay (LOS) was the main outcome measure. Secondary outcome measures were patient and graft survival, post-operative liver graft and kidney function, and transplant cost (reported in relative units [RU]). The patient population consisted of 1,060 consecutive recipients who underwent primary LT at our institution. The first cohort included 643 patients transplanted between September 2002 and March 2006 (“Study Cohort”- SC). This cohort was used to identify risk factors for poor outcome and construct a mathematical model to identify patients with expected inferior results. Mean patient follow-up was 40.5 ± 0.8 months. The second cohort consisted of 417 patients transplanted from April 2006 to December 2009. This cohort was used for validation of the model (“Validation Cohort”- VC). Validation was done by calculating the probability of adverse outcome (LOS>60) and comparing the actual hospital stay, patient and graft survival and transplant cost of the patients with the highest score (53 patients; 12.7%) to those of the rest of the VC. Mean patient follow-up was 54.8 ± 1.3 months. Results: In the SC of 643 patients, post-operative LOS ranged from 1 to 209 days with a mean and median of 27.7 and 16 days, respectively. Sixty five patients (10.1%) had LOS > 60 days. One- and three-year patient/graft survival rates were 81.9%/76.1% and 73.4%/67.4%, respectively. Patient and graft survival of those with LOS >60 days were significantly inferior (p < 0.0001) while the cost of transplantation was significantly greater (3.42 RU vs. 1 RU, p < 0.0001), when compared to those with hospital LOS ≤ 60 days. In a multivariable analysis, recipient pre-transplant dialysis (p< 0.001), mechanical ventilation (p< 0.015), MELD score (p< 0.003) and age (p< 0.009) were independent predictors of LOS > 60 days. The ROC curve of the model prognosticating hospital LOS > 60 days was 0.75 (95% CI [0.70, 0.81]). In the validation phase of the study, 53 patients (12.7%) were expected to have adverse outcome by the model. These patients had significantly longer LOS (48.5±4.5 vs. 25.6±1.3 days; p < 0.0001), higher cost (1.53 RU vs. 1; p < 0.0001) and inferior patient and graft survival (1 and 3 years survival of 71.7% and 64.2% vs. 87.6% and 79.2%; p< 0.007). Conclusions: Older patients with the combination of advanced MELD score, in need of mechanical ventilation and renal replacement therapy, are prone to prolonged and expensive hospital stay and significantly inferior patient and graft survival. Using the proposed model, allows for identification of candidates with high probability of poor outcome.