Serum surfactant protein D: Biomarker of chronic obstructive pulmonary disease

Background: Surfactant protein D (SP-D) is a lung-specific protein proposed to predict clinical outcomes in patients with chronic obstructive pulmonary disease (COPD). However, the changes in serum SP-D during acute exacerbation (AECOPD) episodes and the relationship of serum SP-D with the overall severity of the disease in stable COPD (SCOPD) remain unclear. Methods: Serum SP-D levels were analyzed in three groups, including AECOPD ( n = 40), SCOPD ( n = 71), and controls ( n = 60). In AECOPD group, serum SP-D levels were determined at 1, 5, 14, and 30 days post-exacerbation. In SCOPD group, BODE (body mass index, airflow obstruction, dyspnea, exercise capacity) index was evaluated for severity assessment. Results : Serum SP-D levels were sequentially elevated from the controls to the SCOPD, and then to the AECOPD ( p p > 0.05), fell markedly at day 14 ( p p p Conclusions: The longitudinal changes in s erum SP-D levels during an AECOPD episode suggest that SP-D may be a potential systemic biomarker for COPD exacerbation. The correlation of serum SP-D levels with the BODE index suggests that circulating SP-Ds can reflect the overall severity of SCOPD.