Early diagnostic value of serum S100 calcium-binding protein A12, serum amyloid A protein, and neutrophil-to-lymphocyte ratio in patients with acute empyema.

Acute empyema refers to suppurative inflammation of the pleural cavity secondary to pulmonary infection. Prompt diagnosis and intervention are required upon identification to prevent progression to chronic empyema; hence, clinically effective biomarkers are needed to predict the development of acute empyema. To investigate the early diagnostic value of four serum markers, namely, S100 calcium-binding protein A12 (S100A12), serum amyloid A (SAA), C-reactive protein (CRP), and neutrophil-to-lymphocyte ratio (NLR), for predicting progression to acute empyema in patients with early-stage pneumonia. A retrospective analysis was performed on 60 patients diagnosed with community-acquired pneumonia complicated with acute empyema admitted to Xichang People's Hospital from January 2021 to June 2022. Another 60 patients with community-acquired pneumonia without empyema treated during the same period were enrolled as controls. Univariate analysis was used to compare differences in general clinical data, clinical manifestations, biochemical indicators, and treatment conditions between the two groups. Receiver operating characteristic (ROC) curves were adopted to evaluate differences in sensitivity and specificity of single and combined detection of S100A12, SAA, and NLR for early identification of acute empyema. Levels of S100A12, SAA, CRP, and NLR were significantly higher in patients with acute empyema than in those with community-acquired pneumonia (all P < 0.05), whereas serum albumin was markedly lower in the empyema group (P < 0.05). ROC curve analysis was performed to assess the diagnostic efficacy of individual and combined S100A12, SAA, and NLR for predicting acute empyema. The combined panel of S100A12+SAA+NLR yielded a sensitivity of 76.7% and a specificity of 96.7%, with an area under the ROC curve (AUROC) of 0.938 (95% CI: 0.900-0.977, P < 0.0001). The AUROC of the combined panel was significantly superior to those of single S100A12 (AUROC = 0.803, 95% CI: 0.722-0.884, P < 0.0001), SAA (AUROC = 0.908, 95% CI: 0.860-0.957, P < 0.0001), and NLR (AUROC = 0.694, 95% CI: 0.599-0.788, P = 0.0003), with statistically significant differences (P < 0.05). Acute empyema is mostly secondary to pulmonary infection, which is closely associated with host immunity, bacterial virulence, and invasiveness. Clinicians need reliable predictive biomarkers for early identification and prevention of acute empyema progression. Our study reveals that the combined panel of S100A12, SAA, and NLR achieves favorable sensitivity and specificity in predicting acute empyema, exhibiting superior diagnostic performance for early detection and promising clinical application prospects.