Renal angina index as a predictor of acute kidney injury in critically ill children

Background: Acute kidney injury is associated with increased morbidity and mortality in hospitalized children. In the critically ill, acute kidney injury (AKI) is prevalent and difficult to diagnose. Using conventional methods, AKI is often missed thus delaying the diagnosis up to 48 hours after initial injury. Though some biomarkers that identify AKI early have been identified, they may still be insufficient due to prohibitive costs. Renal angina index is used to identify ongoing renal injury. It is a product of the clinical state and the estimated glomerular filtration rate (eGFR) of a patient during admission to a critical care unit. An inexpensive tool to predict AKI could have large impact on the outcomes of critically ill children. Other biomarkers for early diagnosis of AKI are expensive and inaccessible to most clinicians in low- and middle-income countries. Diagnosis of AKI on day one as opposed to day three when it is typically diagnosed may reduce the morbidity and mortality associated with AKI in critically ill children. Renal angina index (RAI) is a promising such tool but requires validation in the sub-Saharan African setting. This study may provide the evidence required to consider RAI as a routine screening tool for AKI in critical care admissions. Primary Objective: To determine the utility of Renal Angina Index in the diagnosis of acute kidney injury in critically ill children Secondary Objective: To determine utility of renal angina index in prediction of short-term outcomes of patients admitted to critical care units. Methods: Eighty-nine critically ill children aged between one month and 14 years of age admitted in the critical care unit were recruited. Demographic and anthropometric data, indication for admission and serum creatinine level were obtained at the time of admission. Renal angina index for each participant were calculated. Patients were followed up for 72 hours and serum creatinine measured on third day of admission. Kidney Disease Improving Global Outcomes (KDIGO) definition of AKI was used to determine the presence or absence of AKI using the serum creatinine level obtained on third day of admission. Sensitivity, specificity, positive predictive value, negative predictive value and area under the curve (AUC) on a receiver operating characteristics (ROC) curve were calculated to determine diagnostic utility of the renal angina index. Results: Using an initial cut-off of 8.0, RAI had sensitivity, specificity, positive predictive value and negative predictive values of 57.9%, 90.0%, 61.1% and 88.7% respectively. With adjusted cut-off at 7.0, the sensitivity, specificity, PPV and NPV were 78.9%, 84.3%, 57.7% and 93.7% respectively. The area under the curve (AUC) was 0.855 (95% CI; 0.751-0.959). The relative risk for death with a positive RAI at admission was 7.72 (95% CI; 2.67-22.27) times higher than RAI negative group while relative risk for undergoing dialysis was 13.15 (95% CI; 4.03-42.87) times higher in patients with admission RAI positive. Conclusion: When a cut-off of 7.0 is used, Day-1 Renal angina index has acceptable sensitivity and specificity in predicting day-3 acute kidney injury in critically ill children. Renal angina index correlates well with mortality and relative risk for undergoing dialysis