Abstract
Community-acquired pneumonia (CAP) remains a leading cause of morbidity and mortality, particularly in older adults. Accurate risk assessment of patients with CAP in the emergency department (ED) is essential for guiding clinical decision-making. This study evaluated the prognostic value of serum amyloid A (SAA) levels for predicting 30-day mortality in patients with CAP presenting to the ED. The data of 398 adult patients with CAP who were admitted to the ED between November 2022 and March 2025 were retrospectively analyzed. Clinical parameters, laboratory biomarkers, and Pneumonia Severity Index (PSI) score were assessed. The primary endpoint was all-cause mortality within 30 days. The overall 30-day mortality rate was 15.8%. SAA levels at ED admission were markedly increased in nonsurvivors compared with those in survivors and demonstrated positive correlations with PSI score and other biomarkers. The area under the curve (AUC) value for SAA levels in predicting mortality was 0.768, which was higher than those for procalcitonin (AUC = 0.671) and high-sensitivity C-reactive protein (AUC = 0.657). The optimal cutoff value for SAA levels was determined to be 280.2 mg/L, yielding a sensitivity of 79.4% and a specificity of 68.5%. Multivariate analysis identified SAA level > 280.2 mg/L, PSI score > 125, intensive care unit admission, and presepsin level > 373 pg/mL as independent predictors of mortality. Thus, increased SAA levels at the time of ED presentation are independently associated with mortality in patients with CAP and may serve as a valuable prognostic biomarker to inform clinical decision-making.