Associations of Serum Clara Cell Protein 16 with Severity and Prognosis in Adults with Community-Acquired Pneumonia.

Background: Clara cell protein 16 (CC16) has multiple functions, including antioxidant, anti-inflammatory, and immune regulation properties. Nevertheless, the concrete function of CC16 in adult patients with community-acquired pneumonia (CAP) remained blurred. Methods: A total of 541 adult patients with CAP were recruited on admission. Peripheral blood specimens, clinical parameters, and demographic characteristics were collected. The concentration of serum CC16 was evaluated through ELISA. The relationships between serum CC16 and clinical parameters were appraised by Spearman or Pearson correlative analyses. The correlations of serum CC16 with severity and prognosis were assessed using linear or logistic regression models. Results: The level of CC16 was gradually decreased across with the elevated severity scores system of CAP. After treatment, the level of serum CC16 was upregulated. Correlative analyses found that serum CC16 was negatively related to inflammatory cytokines. Additionally, multivariate linear and logistic regression models revealed that serum CC16 was inversely associated with severity scores system. In addition, reduced serum CC16 on admission elevated the risks of vasoactive agent usage, ICU admission, and death during hospitalization. We observed an almost discriminatory ability for severity and death between serum CC16 and severity scores system, and were all obviously elevated compared to routine inflammatory and infectious markers. Conclusion: There are substantially inverse correlations between serum CC16 level on admission with severity scores and poorly prognostic outcomes, indicating that CC16 is involved in the pathophysiological process of CAP. This study is helpful for establishing the potential application of serum CC16 in risk evaluation and targeted treatment.