Prognostic value of the lactate-to-albumin ratio for ICU mortality: comparison with lactate, troponin, and APACHE II

Early mortality risk stratification is essential in critically ill patients. Although established severity scores such as the Acute Physiology and Chronic Health Evaluation II (APACHE II) provide valuable prognostic information, simple and readily available biomarkers may complement clinical risk assessment. This study aimed to evaluate the prognostic performance of the lactate-to-albumin ratio (LAR) for intensive care unit (ICU) mortality and to compare its discriminatory ability with lactate, troponin, and APACHE II. This retrospective study included 552 adult patients admitted to the ICU between January 2023 and December 2025. Demographic characteristics, comorbidities, APACHE II and Charlson Comorbidity Index scores, and laboratory parameters obtained at ICU admission were retrospectively recorded. LAR was calculated by dividing serum lactate by serum albumin. Patients were classified as survivors or non-survivors according to ICU outcome. Receiver operating characteristic (ROC) curve analysis was used to evaluate the discriminatory performance of LAR, lactate, albumin, troponin, and APACHE II for ICU mortality. Of the 552 patients, 405 were survivors and 147 were non-survivors. LAR was significantly higher in non-survivors than in survivors [0.85 (0.60–1.59) vs. 0.60 (0.46–0.81), p < 0.001]. APACHE II demonstrated the highest discriminatory performance for ICU mortality (AUC = 0.876, 95% CI: 0.845–0.908), followed by troponin (AUC = 0.754, 95% CI: 0.711–0.797), LAR (AUC = 0.714, 95% CI: 0.664–0.764), and lactate (AUC = 0.708, 95% CI: 0.657–0.758). The cohort-derived optimal LAR cut-off was ≥ 0.759, with 60.5% sensitivity and 71.6% specificity. DeLong analysis showed no significant difference between the AUCs of LAR and lactate ( p = 0.582), whereas APACHE II had significantly greater discriminatory performance than LAR ( p < 0.001). In multivariable logistic regression, LAR remained independently associated with ICU mortality after adjustment for age, APACHE II, Charlson Comorbidity Index, troponin, and admission diagnosis (aOR = 1.526, 95% CI: 1.012–2.301, p = 0.044). LAR was significantly higher among non-survivors and remained independently associated with ICU mortality after adjustment for relevant clinical factors. Although LAR demonstrated moderate discriminatory ability and did not outperform lactate alone, it may provide complementary prognostic information for early mortality risk stratification in critically ill patients. APACHE II showed significantly greater discriminatory performance than LAR. Prospective multicenter studies with external validation are needed to confirm the incremental prognostic value of LAR and establish clinically applicable cutoff values.