Neutrophil-lymphocyte ratio is associated with all-cause mortality among critically ill patients with acute kidney injury

Abstract

Background: Inflammation plays a critical role in the development of acute kidney injury (AKI). Neutrophil-lymphocyte ratio (NLR) is a biomarker of systemic inflammation used to predict the prognostic outcome of several diseases. We conducted a retrospective cohort study to investigate if NLR can be used as a biomarker to predict the mortality of AKI.

Methods and results: Records of critically ill patients with AKI were extracted from the Medical Information Mart for Intensive Care Database III version 1.3 (MIMIC-III v1.3). The primary outcome was 30-day mortality and the two secondary outcomes were in hospital and 90-day mortality. We used the Cox proportional hazards models to assess the association between different categories of NLR and outcomes. This analysis included data for 13,678 eligible subjects, with a total of 2,588 30-day, 2,224 in-hospital and 3,545 90-day deaths during the follow-up period. For 30-day mortality, an increased risk of mortality was associated with a higher level of NLR. The HR (95% confidence interval [CI]) of upper tertile (NLR > 12.14) was 1.37 (1.17-1.60) in a multivariate model when compared with that of the lower tertile (NLR < 5.55). In the quintile analysis, we confirmed the upward trend with HR (95% CI) of the fifth quintile (NLR > 17.4) of 1.35 (1.08, 1.69) in a multivariate model compared to the first quintile (NLR < 3.82). A similar tendency was observed for 90-day mortality. In the analysis of in-hospital mortality, the HR of fifth quintile (NLR > 17.4) showed a slight decrease.

Conclusions: Our analysis indicates that a higher level of NLR is associated with increased risk of 30-day and 90-day mortality in AKI patients. The similar upward trend is not detected in analysis of in-hospital mortality.

Keywords: AKI; Acute kidney injury; ICU; Intensive care unit; Mortality; NLR; Neutrophil-lymphocyte ratio.