Serum cystatin C as a potential biomarker for the evaluation COPD.

BACKGROUND Imbalance between protease-antiprotease plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Cystatin C in circulating blood is a cysteine protease inhibitor and contributes to elastolysis and tissue destruction. OBJECTIVES The aims of the present study were to investigate whether cystatin C was a promising biomarker for the evaluation and follow-up of patients with COPD. METHODS Serum cystatin C level was determined in groups of acute exacerbation of chronic obstructive pulmonary disease (AECOPD) (n = 93), stable COPD (SCOPD) (n = 299) and healthy controls (n = 151). The influences of smoking on the level of serum cystatin C and the correlation of cystatin C with lung functional parameters were further analyzed. RESULTS Serum cystatin C level was significantly higher in COPD patients than that of healthy controls. Smoking increased serum cystatin C level in patients with SCOPD but not in AECOPD and control. In SCOPD group, serum cystatin C level was positively correlated with RV%TLC and negatively correlations with FEV1% predicted, FEV1%FVC, MMEF75/25% predicted, MVV% predicted and DLco% predicted. In multiple line analysis, FEV1% predicted and age were found to be independent predictors of serum cystatin C levels, but not smoking statue, sex and BMI. CONCLUSIONS COPD had a higher level of serum cystatin C, smoking only increased cystatin C level in SCOPD. Serum cystatin C level was negatively correlated with FEV1% predicted. These results suggest that cystatin C might be a potential biomarker for lung tissue destruction and severity of COPD.