Analysis of novel predictors of acute kidney injury after non-cardiac surgery: an integrative review

ABSTRACT Introduction: Acute kidney injury (AKI) is a common postoperative complication (postoperative AKI, [PO-AKI]), occurring in up to 35% of non-cardiac surgery. Some biomarkers have shown value in early identification but are underused in clinical practice due to their high cost. The SPARK score and the hemoglobin-to-red cell distribution width ratio (Hb/RDW) have emerged as accessible alternatives for predicting PO-AKI. Objective: To evaluate studies on SPARK predictors and hematological biomarkers for risk stratification of PO-AKI in non-cardiac surgery. Methods: An integrative review was conducted across four databases (PubMed/MEDLINE, LILACS, Embase, and Web of Science), covering publications between 2019 and 2025 in Portuguese and English. Studies including adults undergoing non-cardiac surgery were included. The selection process was documented using a PRISMA 2020 flow diagram. Results: Six studies were included. The SPARK score showed an AUC ranging from 0.69 to 0.81 in external validations, with superior performance in modified models for specific populations. The Hb/RDW index demonstrated good accuracy (AUC 0.714; sensitivity 72.7%; specificity 70.8%) in elderly orthopedic patients, with lower values associated with increased risk of PO-AKI. Discussion: The effectiveness of SPARK depends on the population profile, highlighting the importance of external validation and contextual adjustments. Hb, RDW, and the Hb/RDW ratio appear to be promising tools to complement SPARK. Conclusion: The application of SPARK may be limited in different contexts. Simple biomarkers such as Hb, RDW, and Hb/RDW show good predictive potential and may improve the early identification of patients at risk for PO-AKI.