The neutrophil-to-lymphocyte ratio as a predictive marker for acute kidney injury in hospitalized sepsis patients: a prospective cohort study

BACKGROUND: Sepsis-associated acute kidney injury (SA-AKI) is a frequent and severe complication of sepsis that substantially increases morbidity and mortality. The neutrophil-to-lymphocyte ratio (NLR), obtained from routine complete blood counts, has emerged as a potential early inflammatory marker; however, its predictive value for SA-AKI remains insufficiently characterized, particularly in real-world hospital settings in Southeast Asia. This study aimed to evaluate the predictive performance of admission NLR for SA-AKI in hospitalized patients with sepsis. METHODS: In this prospective, single-center cohort study, 112 adult patients meeting Sepsis-3 criteria were consecutively enrolled at a tertiary hospital in Thailand between July 2024 and February 2025. Admission NLR was derived from the first routine complete blood count obtained within 24 h of admission. The primary outcome was the development of AKI within 7 days, defined by Kidney Disease: Improving Global Outcomes (KDIGO) creatinine criteria. Receiver operating characteristic (ROC) analysis evaluated the predictive performance of NLR alone and in combination with routinely available clinical variables. Multivariable logistic regression was performed to adjust for clinically relevant covariates. RESULTS: The mean age of the cohort was 77 ± 11 years, and 32 patients (28.6%) developed AKI. Admission NLR was significantly higher in patients who developed AKI than in those who did not (median 20.2 [IQR 11.9-47.3] vs. 9.1 [IQR 5.1-14.3]; P < 0.001). An NLR cut-off of ≥ 12.8 predicted AKI with an area under the curve (AUC) of 0.78 (95% CI 0.69-0.88), sensitivity of 75.0%, and specificity of 72.5%. In multivariable analysis, NLR (adjusted odds ratio [aOR] 5.01, 95% CI 1.75-14.35; P = 0.003) and serum albumin (aOR 0.19, 95% CI 0.06-0.58; P = 0.004) were independently associated with AKI. Combining NLR with serum albumin improved model discrimination, yielding an AUC of 0.83 (95% CI 0.73-0.93). Patients with AKI had a significantly longer hospital stay than those without AKI (median 11 [IQR 6-14] vs. 7 [IQR 4-10.5] days; P = 0.039). CONCLUSIONS: Admission NLR is independently associated with the development of SA-AKI and demonstrates moderate predictive performance for early risk stratification. Integration of NLR with serum albumin further improves model discrimination. These findings support the potential role of routinely available inflammatory and nutritional indices for SA-AKI risk stratification; however, external validation of the NLR cut-off in independent multicenter cohorts is warranted before routine clinical adoption.