Predictive and prognostic value of the neutrophil-to-lymphocyte ratio for acute kidney injury: a systematic review and meta-analysis

Abstract

The neutrophil-to-lymphocyte ratio (NLR) has been suggested as a potential biomarker for the prediction and risk stratification of acute kidney injury (AKI), but conflicting results were reported by literature. We therefore conducted a pooled analysis to consolidate available evidence regarding the predictive and prognostic value of NLR in AKI patients. A systematic search was performed in the PubMed/Medline, Embase, and Cochrane Central Register of Controlled Trials (Central) databases from inception to March 2025 for cohort studies investigating the association between NLR and AKI. Quality assessment was performed via the Quality Assessment for Studies of Diagnostic Accuracy (QUADAS-2) tool. The predictive and prognostic value of the NLR for AKI was evaluated via pooled estimates of odds ratio (OR), sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NeLR), diagnostic score (DS), diagnostic odds ratio (DOR), summary receiver operating characteristic (SROC) curves, and the Fagan nomogram. Twenty-nine studies with 102,870 patients were pooled in this meta-analysis. Higher NLR was associated an increased risk of AKI (OR 1.52, 95% CI 1.29-1.79; p < 0.001). The pooled sensitivity and specificity were 0.70 (95% CI 0.65-0.74) and 0.67 (95% CI 0.60-0.74). The combined values of the PLR, NeLR, DS, and DOR were 2.13 (1.74-2.60), 0.45 (0.38-0.52), 1.56 (1.24-1.89), and 4.78 (3.46-6.60), respectively, with a pooled area under the curve (AUC) for the SROC being 0.74 (95% CI 0.70-0.78). Subgroup analysis suggested that the associations remained statistically significant in contrast-associated AKI (p < 0.001) and surgery-associated AKI (p < 0.001), but of boarder line significance in sepsis-associated AKI (p = 0.082). In addition, higher NLR was also found to be related to 1.47-fold increase in mortality among AKI patients (OR 1.47, 95% CI 1.13-1.91, p = 0.004). NLR is not only an effective marker for predicting AKI event, but also a prognostic tool to identify AKI patients with higher risk of death. Future studies are needed to justify its value in different AKI subtypes.

Keywords: Acute kidney injury; Biomarker; Diagnosis; Neutrophil-to-lymphocyte ratio; Prognosis.

Fig. 1

Flow diagram of the study selection process

Fig. 2

Forest plot of the predictive value of the NLR for AKI. NLR neutrophil-to-lymphocyte ratio, AKI acute kidney injury

Fig. 3

Forest plot of the sensitivity and specificity of the NLR for the prediction of AKI. NLR neutrophil-to-lymphocyte ratio, AKI acute kidney injury

Fig. 4

SROC curve of the NLR for the included studies. SROC summary receiver operating characteristic, NLR neutrophil-to-lymphocyte ratio

Fig. 5

Subgroup analysis of AKI for the predictive value of the NLR. NLR neutrophil-to-lymphocyte ratio, AKI acute kidney injury

Fig. 6

Forest plot of the prognostic value of the NLR for mortality in AKI patients. NLR neutrophil-to-lymphocyte ratio, AKI acute kidney injury