Derivation of a Predictive Model for Graft Loss Following Acute Kidney Injury in Kidney Transplant Recipients

Abstract

Background:Acute kidney injury (AKI) is common in the kidney transplant population.Objective:To derive a multivariable survival model that predicts time to graft loss following AKI.Design:Retrospective cohort study using health care administrative and laboratory databases.Setting:Southwestern Ontario (1999-2013) and Ottawa, Ontario, Canada (1996-2013).Patients:We included first-time kidney only transplant recipients who had a hospitalization with AKI 6 months or greater following transplant.Measurements:AKI was defined using the Acute Kidney Injury Network criteria (stage 1 or greater). The first episode of AKI was included in the analysis. Graft loss was defined by return to dialysis or repeat kidney transplant.Methods:We performed a competing risk survival regression analysis using the Fine and Gray method and modified the model into a simple point system. Graft loss with death as a competing event was the primary outcome of interest.Results:A total of 315 kidney transplant recipients who had a hospitalization with AKI 6 months or greater following transplant were included. The median (interquartile range) follow-up time was 6.7 (3.3-10.3) years. Graft loss occurred in 27.6% of the cohort. The final model included 6 variables associated with an increased risk of graft loss: younger age, increased severity of AKI, failure to recover from AKI, lower baseline estimated glomerular filtration rate, increased time from kidney transplant to AKI admission, and receipt of a kidney from a deceased donor. The risk score had a concordance probability of 0.75 (95% confidence interval [CI], 0.69-0.82). The predicted 5-year risk of graft loss fell within the 95% CI of the observed risk more than 95% of the time.Limitations:The CIs of the estimates were wide, and model overfitting is possible due to the limited sample size; the risk score requires validation to determine its clinical utility.Conclusions:Our prognostic risk score uses commonly available information to predict the risk of graft loss in kidney transplant patients hospitalized with AKI. If validated, this predictive model will allow clinicians to identify high-risk patients who may benefit from closer follow-up or targeted enrollment in future intervention trials designed to improve outcomes.

The effect of cause, timing, kidney function recovery, and recurrent events on the prognosis of acute kidney injury in kidney transplant recipients

“…However, these patients still have increased risk compared to patients without AKI. These results confirm the results of Molnar et al and are in line with the observation that poor graft function at discharge is associated with a poor long‐term graft survival in patients with delayed graft function (DGF) . The increased risk despite the reversibility of AKI is consistent with the results of Uchino, who found increased mortality in patients with a reversible transient GFR reduction regardless of the etiology or the treatment.…”

“…Surprisingly, AKI has a borderline association with worse prognosis (HR: 1.71, 95% CI: 0.99‐2.58) when it occurs during the first 3 months and has more deleterious effect of prognosis when occurring later than 3 months post‐transplantation. A similar result was observed in the study of Molnar et al of kidney transplanted inpatients with AKI . A possible explanation for this intriguing finding may derive from the earlier and more intensive treatment usually given in the setting of early‐onset AKI among kidney‐transplanted patients, as compared to late‐onset AKI.…”

“…AKI can be defined by using discharge codes, as in the study of Mehrotra et al, or by SCr elevation, as in the studies of Nakamura et al, Panek et al, Nagarajan et al, Molnar et al, and our study. The former option can screen a very large population, but captures only AKI events in hospitalized patients, and therefore underestimates the true incidence of AKI.…”

“…In another study, Mehrotra et al reported an incidence of AKI, as defined by the ICD‐9CM codes, of 11.3%, in kidney transplant recipients admitted to the hospital more than 6 months after transplantation. Several other studies evaluated the incidence of AKI in patients after kidney transplantation . These studies were limited by relatively small sample size and selective population or time frame.…”

Acute Kidney Injury in Children with Kidney Transplantation

“…transplant studies showing that deceased donor transplantation is associated with AKI (22,44). Several studies reported a higher incidence of AKI in subjects with CKD and a higher risk of developing AKI with advanced CKD (20)(21)(22)45,46).…”