EXPRESS: Association between serum lactate/albumin ratio and all-cause mortality in critically ill patients: a meta-analysis

Lactate and albumin are routine biomarkers reflecting tissue perfusion and nutritional/inflammatory status, respectively. The serum lactate/albumin ratio (LAR), as a composite indicator, may complement single-parameter measures in disease assessment. However, its association with all-cause mortality in critically ill patients lacks systematic quantification across broad populations. We searched PubMed, Embase, Cochrane Library, and Web of Science through February 18, 2025, for observational studies linking LAR to all-cause mortality in critically ill adults. Two investigators independently selected studies, extracted data, and assessed quality. Hazard Ratios (HR) were pooled for survival analysis, and diagnostic accuracy measures were synthesized using Stata 15.1. The certainty of evidence was rated using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. A total of 29 studies comprising 39,681 patients were included. Elevated LAR was significantly associated with increased short-term (HR 2.63, 95% confidence interval (CI): 2.27-3.04) and long-term all-cause mortality (HR 2.21, 95% CI: 1.70-2.86). Pooled sensitivity, specificity, and summary area under the curve were 0.71 (95% CI: 0.64-0.77), 0.74 (95% CI: 0.69-0.78), and 0.78 (95% CI: 0.75-0.82), respectively, indicating moderate-to-good predictive performance. Subgroup analyses confirmed stability across countries, data sources, disease types, and measurement times. GRADE certainty was high for short-term mortality and low for long-term mortality and diagnostic accuracy. In conclusion, elevated LAR was associated with increased short-term (high-certainty) and long-term mortality (low-certainty) in critically ill patients. Given its accessibility and low cost, LAR may complement established scoring systems for early risk stratification, though prospective validation and standardised cut-offs are needed.