Abstract: Objective To investigate the predictive value of the neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), platelet-to-lymphocyte ratio (PLR), and red blood cell distribution width-to-platelet ratio (RPR) combined with simplified acute physiology score Ⅱ (SAPS Ⅱ)for the 90-day prognosis of elderly patients with sepsis-associated acute kidney injury (SA-AKI). Methods Based on the MIMIC-Ⅳ 2.2 database, a retrospective analysis was conducted on 4589 elderly SA-AKI patients admitted to the ICU for the first time from 2008 to 2019. According to their 90-day outcome, the patients were divided into a survival group (n=2978) and a death group (n=1611). Univariate and multivariate Cox regression analysis were used to identify independent risk factors for prognosis. The predictive performance of each indicator and combined models for the 90-day prognosis was assessed using the area under the receiver operating characteristic (ROC) curve (AUC). Results Multivariate Cox regression analysis showed that NLR, LMR, RPR, 24-hour urine output, lactate, blood urea nitrogen (BUN), and the SAPS Ⅱ were independent risk factors for 90-day mortality in elderly SA-AKI patients (P<0.05). ROC curve analysis revealed that the combined model of NLR+LMR+RPR+SAPS Ⅱ had an AUC of 0.717 (95%CI: 0.701-0.733) for predicting 90-day prognosis, which was significantly higher than the AUC of 0.692 (95%CI: 0.676-0.709) for the model combining BUN+24-hour urine output+SAPS Ⅱ (DeLong’s test, P<0.001). Conclusions The combination of complete blood count-derived ratios (NLR, LMR, RPR) and SAPS Ⅱ has good predictive value for the 90-day prognosis of SA-AKI patients, outperforming the model combining traditional kidney injury markers and SAPS Ⅱ.

Key words: sepsis-associated acute kidney injury, aged, neutrophil-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, red blood cell distribution width-to-platelet count ratio, prognosis, MIMIC-Ⅳ database, simplified acute physiology score