Alpha-1 antitrypsin as a new biomarker of inflammation, infection and disease severity in community-acquired pneumonia: a prospective cohort study.

Alpha-1 antitrypsin (α1-AT), an acute-phase protein, demonstrates anti-inflammatory, antiviral, and immunomodulatory properties. The early detection of disease severity and pathogen in community-acquired pneumonia (CAP) is crucial for patient management. The role of α1-AT in this context has not been fully elucidated. Our study compared plasma α1-AT levels between 74 CAP patients and 86 healthy controls. We measured plasma α1-AT concentrations via ELISA, assessed disease severity using CURB-65, CRB-65, and SMART-COP scores, and analyzed correlations between α1-AT levels with inflammatory markers, disease severity, and pathogen subtypes. Our findings revealed that plasma α1-AT was higher in CAP patients than in controls (p < 0.0001) and correlated positively with IL-6 and TNF-α. In addition, α1-AT concentrations increased with CAP severity and were positively correlated with CURB-65, CRB-65, and SMART-COP scores. Exploratory analyses revealed elevated α1-AT in Gram-positive bacterial and mycoplasma infections, with high predictive value for Gram-positive cases (AUC 0.9479; 95% CI 0.8997-0.9961). These findings suggest α1-AT as a potential adjunctive biomarker for assessing inflammation and disease severity in CAP, while its role in pathogen discrimination requires validation in larger cohorts.