Can We Really Predict Postoperative Acute Kidney Injury after Aortic Surgery? Diagnostic Accuracy of Risk Scores Using Gray Zone Approach

Abstract

Background Several risk scores have been developed to predict acute kidney injury (AKI) after cardiac surgery. We evaluated the accuracy of eight prediction models using the gray zone approach in patients who underwent aortic surgery. Patients and Methods We retrospectively applied the risk scores of Palomba, Wijeysundera, Mehta, Thakar, Brown, Aronson, Fortescue, and Rhamanian to 375 consecutive adult patients undergoing aortic surgery with cardiopulmonary bypass. The area under the receiver operating characteristic curve (AUC) and gray zone approach were used to evaluate the accuracy of the eight models for prediction of AKI, as defined by the RIFLE criteria. Results The incidence of AKI was 29% (109/375). The AUC for predicting AKI requiring dialysis ranged from 0.66 to 0.84, excluding the score described by Brown et al (0.50). The AUC for predicting the RIFLE criteria of risk and higher ranged from 0.57 to 0.68. The application of gray zone approach resulted in more than half of the patients falling in the gray zone: 275 patients (73%) for Palomba, 221 (59%) for Wijeysundera, 292 (78%) for Mehta, 311 (83%) for Thakar, 329 (88%) for Brown, 291 (78%) for Aronson, 205 (54%) for Fortescue, and 308 (82%) for Rhamanian. Conclusion More than half of the patients in our study sample were in the gray zone of eight scoring models for AKI prediction. The two cutoffs of the gray zone can be used when using risk models. A surgery-specific and more accurate prediction model with a smaller gray zone is required for patients undergoing aortic surgery.

Preoperative plasma growth-differentiation factor-15 for prediction of acute kidney injury in patients undergoing cardiac surgery

“…Third, the CC-ARF score had significantly lower ability to predict AKI-1 to AKI-3 and AKI-3 alone than logistic regression analysis based on the present cohort. This contrasts with some studies showing excellent prediction of AKI using the CC-ARF score [ 7 , 13 ] This, however may at least in part be explained by the fact that the present cohort consisted only of patients undergoing elective surgery, as emergency patients were excluded. Thus, the difference between our model and the CC-ARF score may be less pronounced during real-life conditions.…”

“…Various clinical scores for the prediction of renal dysfunction after cardiac surgery have been developed within recent years and these have highly variable predictive ability [ 7 ]. We tested the CC-ARF score as one of the most popular scores [ 13 ].…”

“…No specific treatment for the prevention of CSA-AKI is available [ 4 ]. This may be related to the multifactorial pathophysiology of this complication [ 5 ], including postoperative factors that are difficult to predict preoperatively [ 6 ], but also to the fact that sparse modalities for preoperative risk stratification are available and that commonly used risk scores have variable prognostic utility in this regard [ 7 ]. However, preoperative identification of patients with a high risk of developing CSA-AKI is a prerequisite for developing strategies to ameliorate or prevent perioperative renal injury.…”

Association Between the Neutrophil/Lymphocyte Ratio and Acute Kidney Injury After Cardiovascular Surgery

“… 4 – 11 , 17 , 18 However, there is a discrepancy in risk factors identified in these studies, and a recent study questioned the predictability of previous risk scores by applying the gray zone approach. 19 Recently, several promising plasma and urine biomarkers reflecting renal injury, including cystatin-C and interleukin-18, have been introduced to facilitate early diagnosis. 20 , 21 However, these biomarkers are costly and not sufficiently validated, it is still necessary to develop a clinically useful and cost-effective risk factor of postoperative AKI.…”

Predictions are difficult…especially about AKI

“…In addition to alerting clinicians and warning patients, they may prove to be useful in selecting patients for future prevention or intervention studies or for identifying those in whom biomarker testing should be undertaken. However, in the ICU, AKI scores usually have a limited role since most patients are considered to be at intermediate risk, especially following emergency or cardiac surgery [10]. Last, "AKI sniffers", although useful in alerting physicians earlier of a deterioration in renal function, have yet to prove their role in improving the process of care or clinically relevant outcomes [11].…”