Prediction of Perioperative Mortality of Cadaveric Liver Transplant Recipients During Their Evaluations

Abstract

Background: There are no instruments that can identify patients at an increased risk of poor outcomes after liver transplantation (LT) based only on their preoperative characteristics. The primary aim of this study was to develop such a scoring system. Secondary outcomes were to assess the discriminative performance of the predictive model for 90-day mortality, 1-year mortality, and 5-year patient survival.

Methods: The study population was represented by 30 458 adults who underwent LT in the United States between January 2002 and June 2013. Machine learning techniques identified recipient age, Model for End-Stage Liver Disease score, body mass index, diabetes, and dialysis before LT as the strongest predictors for 90-day postoperative mortality. A weighted scoring system (minimum of 0 to a maximum of 6 points) was subsequently developed.

Results: Recipients with 0, 1, 2, 3, 4, 5, and 6 points had an observed 90-day mortality of 6.0%, 8.7%, 10.4%, 11.9%, 15.7%, 16.0%, and 19.7%, respectively (P ≤ 0.001). One-year mortality was 9.8%, 13.4%, 15.8%, 17.2%, 23.0%, 25.2%, and 35.8% (P ≤ 0.001) and five-year survival was 78%, 73%, 72%, 71%, 65%, 59%, and 48%, respectively (P = 0.001). The mean 90-day mortality for the cohort was 9%. The area under the curve of the model was 0.952 for the discrimination of patients with 90-day mortality risk ≥10%.

Conclusions: Short- and long-term outcomes of patients undergoing cadaveric LT can be predicted using a scoring system based on recipients' preoperative characteristics. This tool could assist clinicians and researchers in identifying patients at increased risks of postoperative death.

FIGURE 1.

The study flowchart. During the study period, 68 078 patients underwent liver transplant surgery. A total of 32 865 (48.2%) patients were excluded because they did not satisfy the inclusion criteria, 1321 (1.9%) recipients had height or weight values that were implausible for adults, and 762 (1.1%) patients had >10% of variables with missing data or the absence of values for the variables needed to calculate the perioperative mortality risk. In the end, a total of 30 458 fist time cadaveric liver transplant recipients were included in the study.

FIGURE 2.

Observed 90-day mortality stratified by the number of points of the scoring system. For each additional point of the scoring system, the observed 90-day mortality increased in average by 2.3%.

FIGURE 3.

Graphic evaluation of the calibration of the model. Values on the y-axis represent the estimates of 90-day mortality calculated by artificial neural network analysis. Values on the x-axis represent the observed 90-day mortality stratified by risk score. The lowest values of the predicted and observed mortality (left lower quadrant, A) represent patients with 0 or 1 risk score point. Values in the upper right quadrant represent the predicted and observed 90-day mortality of patients with 4, 5, and 6 points (Quadrant C). Patients with 2 and 3 points had predicted and observed 90-day mortality values that fell in between (Quadrant B). The Pearson correlation coefficient (R²) of the model was 0.99 (P < 0.001).

FIGURE 4.

Receiver operating characteristic curves of the model illustrating the discriminating performance of the model to diagnose 90-day mortality of all patients undergoing cadaveric LT (A). B, The area under the curve (AUC) of the model for the prediction of patients with perioperative risk ≥10%, (C) the AUC of the model for the prediction of patients with perioperative risk ≥15%, and (D) the AUC of the model for the prediction of patients with perioperative risk ≥20%. LT, liver transplantation.

FIGURE 5.

Observed 1-y mortality in patients undergoing deceased donor liver transplantation stratified by the scoring system. For each additional point of the scoring system, the observed 1-y mortality increased on average by 4.3%.

FIGURE 6.

Kaplan-Meier survival curves of all adult liver transplant recipients stratified by their risk score. Pairwise comparisons between groups showed statistically significant differences in 5-y survival except when patients with 2 points were compared to patients with 3 points (P = 0.794).