Association of serum surfactant protein-D levels with COPD severity and clinical history.

<bold>Background:</bold> Chronic obstructive pulmonary disease (COPD), characterized by persistent respiratory symptoms and airflow limitation, is a global health concern. Surfactant protein-D (SP-D) is linked to lung inflammation and injury, has drawn attention for its potential role in COPD development. While previous studies suggest an association between SP-D levels and COPD severity, further investigation is needed to elucidate its clinical relevance. <bold>Objectives:</bold> We aimed to measure serum SP-D levels in COPD subjects and explore potential associations with clinical parameters, viz., COPD Assessment Test (CAT) scores, clinical history, and disease severity. <bold>Methods:</bold> We conducted a case-control study with 298 subjects (149 COPD, 149 non-COPD). Baseline characteristics, clinical data (CAT scores, disease severity, and clinical history), and serum were collected from each participant. Serum SP-D levels were measured using an enzyme-linked immunosorbent assay (ELISA). Result: The mean serum level of SP-D was higher in COPD than non-COPD (p<0.0003). Within the COPD cohort, individuals with CAT scores ≥10 exhibited elevated SP-D levels compared to those with scores <10 (p<0.0141). SP-D levels also showed a significant increase from GOLD stages 1+2 to 3+4 (p<0.0001). Additionally, COPD patients with a longer clinical history (≥20 years) displayed higher SP-D levels compared to those with a shorter history (<10 years) (p=0.039). <bold>Conclusion:</bold> Our findings highlight the potential of serum SP-D as a biomarker for COPD severity and progression, warranting further investigation into its clinical utility and mechanistic role in COPD pathophysiology.