Conclusion
In conclusion, circulating SDC-1 may be a novel inflammatory biomarker associated with lung function and systemic inflammation in patients with COPD, which could also be useful to identify the risk of COPD exacerbation. Further studies should be performed to clarify the influences of SDC-1 on the pathogenesis and outcomes of COPD.
Results
Although both serum SDC-1 and SDC-4 showed a downward trend in COPD patients, only SDC-1 levels were correlated positively with the ratio of FEV1/FVC and parameters of small airway obstruction. Besides, SDC-1 but not SDC-4, was negatively correlated with C-reactive protein (CRP) in COPD patients and downregulated in frequent exacerbators (FEs) of COPD. Using a cutoff value of 2.08 ng/mL, the sensitivity and specificity of SDC-1 to differentiate FE were 44% and 93.4%, respectively.