Effect of lactate/albumin ratio on mortality in patients aged ≥ 65 years with community-acquired pneumonia

Abstract

Introduction: Community-acquired pneumonia (CAP) remains a major cause of morbidity and mortality in elderly patients. Early identification of high-risk individuals is crucial for improving outcomes. Biomarkers derived from routine laboratory tests, such as the lactate / albumin (L/A) ratio, may provide valuable prognostic information.

Methodology: This retrospective, two-center observational study included patients aged ≥ 65 years who were hospitalized with CAP between January 2021 and December 2024. Demographic characteristics, comorbidities, clinical severity scores, and laboratory parameters obtained at hospital admission were analyzed. Laboratory-derived ratios, including L/A, C-reactive protein/albumin (CRP/A), procalcitonin/albumin (PCT/A), and lactate dehydrogenase/albumin (LDH/A), were calculated. Receiver operating characteristic (ROC) analysis and logistic regression were performed to assess predictors of in-hospital mortality.

Results: A total of 150 patients were included, of whom 24% died during hospitalization. Non-survivors had significantly higher comorbidity burden, quick sepsis-related organ failure assessment (qSOFA) scores, lactate levels, and biomarker-based ratios. The L/A ratio was significantly associated with mortality (p < 0.001) and demonstrated moderate diagnostic performance (area under ROC, AUC = 0.263), with relatively favorable sensitivity and negative predictive value. Among the evaluated clinical scores, qSOFA showed the most balanced discriminatory performance. Multivariate analysis identified baseline oxygen saturation, Glasgow coma scale, albumin, and lactate levels as independent predictors of mortality.

Conclusions: The L/A ratio is a readily available biomarker associated with mortality in elderly patients with CAP. Although not a standalone predictor, it may serve as a complementary prognostic tool alongside established clinical severity scores, particularly during early patient assessment.