Prognostic value of neutrophil-to-lymphocyte ratio dynamics in patients with septic acute kidney injury: a cohort study

Background: Neutrophil-to-lymphocyte ratio (NLR) has been suggested to be a prognostic marker for various diseases, but whether NLR dynamics (Delta NLR) is related to mortality and disease severity in patients with septic acute kidney injury (AKI) has not been determined. Methods: Between August 2013 and August 2021, septic AKI patients at our center were retrospectively enrolled. Delta NLR was defined as the difference between the NLR at septic AKI diagnosis and at hospital admission. The relationship between the Delta NLR and mortality was evaluated by Kaplan-Meier curves, Cox proportional hazards, and cubic spline analyses. The prediction values were compared by area under the receiver-operating characteristic curve (AUROC), net reclassification improvement (NRI), and integrated discrimination improvement (IDI) analyses. Results: Of the 413 participants, the mean age was 63 +/- 17 years, and 134 were female (32.4%). According to the median value, patients in the high-Delta NLR group had significantly greater 90-d mortality (74.4% vs. 46.6%, p < 0.001). After adjustment for potential confounders, high Delta NLR remained an independent predictor of 90-d mortality (HR = 2.80; 95% CI = 1.74-4.49, p < 0.001). Furthermore, Delta NLR had the highest AUROC for 90-d mortality (0.685) among the various biomarkers and exhibited an improved NRI (0.314) and IDI (0.027) when incorporated with PCT and CRP. For secondary outcomes, patients with high Delta NLR had increased risk of 30-d mortality (p = 0.004), need for renal replacement therapy (p = 0.011), and developing stage-3 AKI (p = 0.040) according to the adjusted models. Conclusions: High Delta NLR is independently associated with increased risk of patient mortality and adverse outcomes. Delta NLR might be utilized to facilitate risk stratification and optimize septic AKI management.