Sepsis-associated acute kidney injury (AKI) is a common and severe complication in critically ill patients and is associated with high mortality. Early identification of patients at high risk of death remains challenging. Lactate reflects tissue hypoperfusion and disease severity, whereas thrombocytopenia is associated with inflammation, coagulation dysfunction, and poor outcomes in sepsis. The lactate-to-platelet ratio (LPR), combining these two parameters, has emerged as a potential prognostic biomarker in critically ill patients. This study aimed to evaluate the prognostic value of LPR for predicting early mortality in patients with sepsis-associated AKI.

We conducted a prospective cross-sectional study involving 173 patients with sepsis-associated AKI admitted to 108 Military Central Hospital between January and December 2023. Clinical characteristics, laboratory findings, severity scores, and LPR values obtained within the first 24 hours of admission were collected. LPR was calculated by dividing serum lactate (mmol/L) by platelet count (G/L).The primary outcome was early mortality, defined as death within four days of ICU admission. Receiver operating characteristic (ROC) curve analysis was performed to assess the predictive performance of LPR and compare it with other prognostic indicators.

Among the 173 enrolled patients, 34 (19.7%) died within four days of ICU admission. Non-survivors had significantly higher SOFA and SAPS II scores and serum lactate level, while platelet count was significantly lower than those of survivors (p < 0.05). Median LPR was markedly elevated in non-survivors compared with survivors (5.81 [2.53–11.82] vs. 1.67 [0.97–4.54], p < 0.01). ROC analysis demonstrated that LPR had the best discriminative ability for predicting early mortality, with an area under the curve (AUC) of 0.76. At a cutoff value of 2.3, LPR showed 82% sensitivity and 63% specificity. LPR outperformed serum lactate (AUC = 0.68), platelet count (AUC = 0.70), SOFA score (AUC = 0.68), and APACHE II score (AUC = 0.61) in predicting early mortality.

LPR is a simple, inexpensive, and readily available biomarker with good prognostic value for predicting early mortality in patients with sepsis-associated AKI. This index may be useful for early risk stratification and clinical decision-making in critically ill patients.