title: Serum functional dickkopf-1 levels are inversely correlated with radiographic severity of ankylosing spondylitis.
abstract: BACKGROUND
  Dickkopf-1 (DKK-1) has been proved dysfunctional in ankylosing spondylitis (AS), and decreased serum functional DKK-1 levels have been identified to be decreased in AS patients. This study aims to examine the relation of binding (functional) DKK-1 levels in serum with the radiographic severity of AS.
  
  
  METHODS
  Total Dkk1 levels were assessed by commercial sandwich enzyme-linked immunosorbent assay and functional DKK-1 levels of serum were measured using functional enzyme-linked immunosorbent assay method in 84 patients with AS and 79 healthy controls. The radiographic progression of AS was classified according to the radiographic events of modified New York Criteria for sacroiliac joints evaluation and modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) system for spine assessment.
  
  
  RESULTS
  No significant difference was seen between AS patients and healthy controls for total Dkk1 levels (p = 0.273). Decreased levels of functional DKK-1 in serum were found in AS patients compared with healthy controls 17.24 (1.24-11.15) vs. 9.15 (5.33-13.35) pg/mL, p < 0.001]. Functional DKK-1 levels in serum of AS patients were significantly associated with the disease radiographic severity evaluated by modified New York grading criteria (r = -0.236, p = 0.04) and mSASSS system (r = -0.389, p = 0.025).
  
  
  CONCLUSIONS
  Serum functional DKK-1 levels showed an independent and negative correlation with radiographic severity of the disease in patients with AS. Functional DKK-1 in serum might serve as a potential biomarker for reflecting the progression of ankylosing spondylitis.
authors.forename: Zou
authors.initials: Z
authors.lastname: Yucong
authors.forename: Lu
authors.initials: L
authors.lastname: Lu
authors.forename: Li
authors.initials: L
authors.lastname: Shengfa
authors.forename: Ye
authors.initials: Y
authors.lastname: Yongliang
authors.forename: Shang
authors.initials: S
authors.lastname: Ruguo
authors.forename: Li
authors.initials: L
authors.lastname: Yikai
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D018450:Disease Progression; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood*; D008297:Male; D011237:Predictive Value of Tests; D011379:Prognosis; D011859:Radiography; D012720:Severity of Illness Index; D013131:Spine / Q000000981:diagnostic imaging*; D013167:Spondylitis, Ankylosing / Q000097:blood* / Q000000981:diagnostic imaging*; D055815:Young Adult
chemical_list: D015415:Biomarkers; C501126:DKK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins