Neutrophil-to-Lymphocyte ratio as a prognostic marker of mortality and disease severity in septic Acute kidney injury Patients: A retrospective study

Abstract

Background: Acute kidney injury (AKI) is a frequent complication of sepsis associated with increased mortality and morbidity. The neutrophil-to-lymphocyte ratio (NLR) has been shown as a risk factor for septic AKI. In this study, we aimed to further evaluate NLR's prediction value on the prognosis of septic AKI patients.

Methods: Septic AKI patients at a tertiary university-affiliated medical center were retrospectively enrolled from August 2015 to August 2021. The primary outcomes were 30-day and 90-day mortality, and secondary outcomes were disease severity, length of stay, and rehospitalization in survivors. Kaplan-Meier curves, Cox proportional hazards, cubic spline and logistics regression analyses were performed for adverse outcomes basing on NLR. The predictive value of NLR on morality was also estimated by the area under the receiver operating characteristic curve (AUROC).

Results: A total of 309 septic AKI patients were included with a mean age of 57.8 ± 18.1 years and 92 (29.8 %) being female. The 30-day mortality was 43.4 % and 90-day morality was 61.8 %. When divided by the median of NLR at hospital admission, patients in the high NLR group were associated with an increased 30-day/90-day mortality. After adjusting for multiple covariates, the predictive value of NLR remained significant for 30-day mortality (HR: 2.96, 95 % CI: 1.48-5.92, p = 0.002) and 90-day mortality (HR: 1.88, 95 % CI: 1.11-3.16, p = 0.018). NLR at admission had the highest AUROC (0.618) for 30-day mortality compared with other parameters such as white blood cell (0.573), neutrophil (0.579), lymphocyte (0.567), platelet (0.546), BUN (0.580), albumin (0.545), C-reactive protein (0.571) and procalcitonin (0.534). A similar predictive value on mortality was also observed for NLR measured at septic AKI diagnosis. For secondary outcomes, high NLR was associated with increased risk of transfer to ICU, mechanical ventilation, stage-3 AKI and renal replacement therapy, but not with length of hospital/ICU stay or long-term rehospitalization.

Conclusion: High NLR is independently associated with 30-day/90-day mortality and disease severity in septic AKI patients. NLR may serve as an economic and widely available biomarker of septic AKI prognosis.

Keywords: Acute kidney injury; Mortality; Neutrophil-to-lymphocyte ratio; Prognosis; Sepsis.