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

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.