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

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.