Single emergency room measurement of neutrophil/lymphocyte ratio for early detection of acute kidney injury (AKI)

Neutrophil-to-lymphocyte ratio (NLR) is considered a readily available biomarker of systemic inflammation. An association between elevated NLR and adverse outcomes in a variety of medical and surgical conditions including CKD has been demonstrated in several studies. In this study, we evaluated the accuracy of single Emergency Department (ED) measurement of NLR for early diagnosis of acute kidney injury (AKI). We prospectively studied 294 patients aged 71.6 ± 17. We measured NLR at presentation to the ED. AKI is defined as a new-onset 1.5-fold or more increase in serum creatinine or a 25% decrease in estimated GFR sustained for at least 3 days despite volume resuscitation. The primary outcome is AKI. Secondary outcome is in-hospital mortality. A multivariate model and ROC analysis were performed to evaluate the association and eventual predictive capacity of NLR for the outcomes. 36 patients (12.2%) developed AKI and 26 (9%) died, 8 (22%) of the AKI group and 17 patients (7%) of the non-AKI group. The Mean NLR is significantly higher in AKI compare to non-AKI patients (11.7 ± 15.2 vs 6.45 ± 7.19, p = 0.048). A multivariate model adjusted for age, gender, blood pressure, plasma albumin and hemoglobin levels confirms that the NLR is higher in AKI patients (p = 0.031). Receiver operating characteristics curve reveals an AUC of 0.715 (95% CI 0.63–0.8) sensitivity 0.78, specificity 0.65, and OR 6.423 (CI 2.659–16.026) for a cutoff value of NLR 5.5. The relation between NLR and in-hospital mortality is not statistically significant (p = 0.92). Single ED measurement of NLR might be a useful tool for early diagnosis of AKI. This finding is particularly important in light of the low cost and widespread availability of NLR, especially compared with other biomarkers currently under study in the context of AKI.