title: Proteoglycan 4 is a diagnostic biomarker for COPD.
abstract: BACKGROUND
  The measurement of C-reactive protein (CRP) to confirm the stability of COPD has been reported. However, CRP is a systemic inflammatory biomarker that is related to many other diseases.
  
  
  OBJECTIVE
  The objective of this study is to discover a diagnostic biomarker for COPD.
  
  
  METHODS
  Sixty-one subjects with COPD and 15 healthy controls (10 healthy non-smokers and 5 smokers) were recruited for a 1-year follow-up study. Data regarding the 1-year acute exacerbation frequency and changes in lung function were collected. CRP and the identified biomarkers were assessed in the validation COPD cohort patients and healthy subjects. Receiver operating characteristic values of CRP and the identified biomarkers were determined. A validation COPD cohort was used to reexamine the identified biomarker. Correlation of the biomarker with 1-year lung function decline was determined.
  
  
  RESULTS
  Proteoglycan 4 (PRG4) was identified as a biomarker in COPD. The serum concentrations of PRG4 in COPD Global initiative for chronic Obstructive Lung Disease (GOLD) stages 1+2 and 3+4 were 10.29 ng/mL and 13.20 ng/mL, respectively; 4.99 ng/mL for healthy controls (P<0.05); and 4.49 ng/mL for healthy smokers (P<0.05). PRG4 was more sensitive and specific than CRP for confirming COPD severity and acute exacerbation frequency. There was no correlation between CRP and PRG4 levels, and PRG4 was negatively correlated with the 1-year change in predicted forced vital capacity percent (R (2)=0.91, P=0.013).
  
  
  CONCLUSIONS
  PRG4 may be a biomarker for identification of severity in COPD. It was related to the 1-year forced vital capacity decline in COPD patients.
authors.affiliation: Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan ; Department of Internal Medicine, School of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Kang-Yun
authors.initials: KY
authors.lastname: Lee
authors.affiliation: Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan ; School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Hsiao-Chi
authors.initials: HC
authors.lastname: Chuang
authors.affiliation: Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan.
authors.forename: Tzu-Tao
authors.initials: TT
authors.lastname: Chen
authors.affiliation: Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan ; School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Wen-Te
authors.initials: WT
authors.lastname: Liu
authors.affiliation: Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan ; School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Chien-Ling
authors.initials: CL
authors.lastname: Su
authors.affiliation: Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan ; Department of Internal Medicine, School of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Po-Hao
authors.initials: PH
authors.lastname: Feng
authors.affiliation: Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan ; School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Ling-Ling
authors.initials: LL
authors.lastname: Chiang
authors.affiliation: School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan ; Division of Pulmonary Medicine, Department of Internal Medicine, Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: Mauo-Ying
authors.initials: MY
authors.lastname: Bien
authors.affiliation: School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Shu-Chuan
authors.initials: SC
authors.lastname: Ho
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis*; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011509:Proteoglycans / Q000097:blood*; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis*; D012372:ROC Curve; D012720:Severity of Illness Index; D013624:Taiwan; D000099158:Proteoglycan 4
chemical_list: D015415:Biomarkers; D002097:C-Reactive Protein; D011509:Proteoglycans; C419197:PRG4 protein, human; D000099158:Proteoglycan 4
keywords: C-reactive protein; exacerbation; inflammation; lung function decline