title: Serum cystatin C as a potential biomarker for the evaluation COPD.
abstract: 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.
  
  
  OBJECTIVE
  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.
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Yonghong
authors: Y
authors: Zhang
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Yanting
authors: Y
authors: Zhu
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Yuanyuan
authors: Y
authors: Wu
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Guizuo
authors: G
authors: Wang
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Xinming
authors: X
authors: Xie
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Rui
authors: R
authors: Ke
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Shaojun
authors: S
authors: Li
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Lu
authors: L
authors: Liu
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Wei
authors: W
authors: Fen
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Fengjuan
authors: F
authors: Li
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Fangxia
authors: F
authors: Li
authors: Department of Respiratory Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University Xi'an 710004, Shanxi, People's Republic of China.
authors: Manxiang
authors: M
authors: Li
keywords: COPD; biomarker; cathepsins; cystatin C; lung function