Prediction of delayed graft function using different scoring algorithms: A single-center experience

Abstract

Aim: To compare the performance of 3 published delayed graft function (DGF) calculators that compute the theoretical risk of DGF for each patient.

Methods: This single-center, retrospective study included 247 consecutive kidney transplants from a deceased donor. These kidney transplantations were performed at our institution between January 2003 and December 2012. We compared the occurrence of observed DGF in our cohort with the predicted DGF according to three different published calculators. The accuracy of the calculators was evaluated by means of the c-index (receiver operating characteristic curve).

Results: DGF occurred in 15.3% of the transplants under study. The c index of the Irish calculator provided an area under the curve (AUC) of 0.69 indicating an acceptable level of prediction, in contrast to the poor performance of the Jeldres nomogram (AUC = 0.54) and the Chapal nomogram (AUC = 0.51). With the Irish algorithm the predicted DGF risk and the observed DGF probabilities were close. The mean calculated DGF risk was significantly different between DGF-positive and DGF-negative subjects (P < 0.0001). However, at the level of the individual patient the calculated risk of DGF overlapped very widely with ranges from 10% to 51% for recipients with DGF and from 4% to 56% for those without DGF. The sensitivity, specificity and positive predictive value of a calculated DGF risk ≥ 30% with the Irish nomogram were 32%, 91% and 38%.

Conclusion: Predictive models for DGF after kidney transplantation are performant in the population in which they were derived, but less so in external validations.

Keywords: Delayed graft function; Kidney transplantation; Nomogram; Receiver operating characteristic curve; Risk calculation.

Figure 1

Receiver operating characteristic curves to evaluate the prognostic capacity of cold ischemia time, the delayed graft function risk calculator, the Jeldres scoring system[10] and the DGFS scoring system[11] to predict delayed graft function. The cold ischemia time (purple-line): Area under ROC curve (AUC) = 0.52. The DGF risk calculator (green-line) proposed by Irish et al[9]: AUC = 0.69. The scoring system (blue-line) proposed by Jeldres et al[10]: AUC = 0.54. The DGFS scoring system (red-line) proposed by Chapal et al[11]: AUC = 0.51. ROC: Receiver operating characteristic; CIT: Cold ischemia time; DGF: Delayed graft function.

Figure 2

Calibration plot of: The delayed graft function risk calculator (Irish et al[9]), the Jeldres scoring system[10] and the DGFS scoring system (Chapal et al[11]) to predict delayed graft function. Patients were divided into 10 subgroups (deciles of increased DGF risk), based upon the risk prediction. Each figure plots the mean predicted probability (X-axis) of DGF against the observed prevalence of DGF (Y-axis) (Hosmer-Lemeshow). The P-values were 0.74 for the Irish score, < 0.05 for the Jeldres score and 0.02 for the Chapal score. DGF: Delayed graft function.

Figure 3

Correlation between the predicted delayed graft function probability according to the delayed graft function risk calculator (Irish et al[9]) and the presence or absence of delayed graft function. DGF: Delayed graft function.

Figure 4

Correlation between the predicted delayed graft function probability according to the Jeldres scoring system (Jeldres et al[10]) and the presence or absence of delayed graft function. DGF: Delayed graft function.

Figure 5

Correlation between the DGFS value (A: Y-axis) and the predicted delayed graft function probability according to the DGFS scoring system (Chapal et al[11]) (B: Y-axis) and the presence or absence of delayed graft function (A and B: X-axis). DGF: Delayed graft function.