title: Plasma and Synovial Fluid CXCL12 Levels Are Correlated With Disease Severity in Patients With Knee Osteoarthritis.
abstract: BACKGROUND
  The aim is to determine whether CXC chemokine ligand-12 (CXCL12) levels in plasma and synovial fluid (SF) of patients with knee osteoarthritis (OA) are correlated with the disease severity. In addition, we set out to investigate whether a peripheral blood test can avoid aspirating patients to determine CXCL12 levels.
  
  
  METHODS
  This study consisted of 244 patients with knee OA and 244 age- and gender-matched healthy controls. Osteoarthritis progression was classified based on Kellgren-Lawrence (KL) by evaluating radiographic changes observed in anteroposterior knee radiography. The CXCL12 levels in the plasma and SF were measured by a quantitative sandwich enzyme-linked immunosorbent assay.
  
  
  RESULTS
  Plasma CXCL12 levels were higher in OA patients as compared with controls (P < .0001). There was a positive correlation between levels of CXCL12 and grade (P < .0001). Base on the receiver operating characteristic curve, the optimal cutoff value of plasma CXCL12 levels as an indicator for screening of OA was estimated to be 5.5 ng/mL, which yielded a sensitivity of 78.4% and a specificity of 80.2%, with the area under the curve at 0.850 (95% confidence interval [CI], 0.816-0.889; P < .0001). In multivariate analysis, there was an increased risk of active OA associated with plasma CXCL12 levels ≥10.5 ng/mL (odds ratio, 6.76; 95% CI, 3.88-12.53; P < .0001) after adjusting for possible confounders. Similarly, there was an increased risk of active OA associated with SF CXCL12 levels ≥15.0 ng/mL (odds ratio, 8.45; 95% CI, 3.23-18.22; P < .0001) after adjusting for possible confounders.
  
  
  CONCLUSIONS
  The CXCL12 levels in the plasma and SF may serve as effective biomarkers for the severity of OA.
authors.affiliation: Department of Orthopedics, the 305 Hospital of Chinese PLA, Beijing, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: He
authors.affiliation: Department of Orthopedics, General Hospital of Chinese Armed Police Forces, Beijing, People's Republic of China.
authors.forename: Mingxin
authors.initials: M
authors.lastname: Wang
authors.affiliation: Department of Orthopedics, Changzheng Hospital of Second Military Medical University, Shanghai, People's Republic of China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Orthopedics, General Hospital of Chinese Armed Police Forces, Beijing, People's Republic of China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Orthopedics, People's Hospital of Poyang Country, Jiangxi Province, People's Republic of China.
authors.forename: Bin
authors.initials: B
authors.lastname: Luo
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000032:analysis / Q000097:blood; D016022:Case-Control Studies; D054377:Chemokine CXCL12 / Q000032:analysis / Q000097:blood*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000097:blood* / Q000000981:diagnostic imaging*; D010949:Plasma / Q000737:chemistry; D011859:Radiography; D012720:Severity of Illness Index; D013582:Synovial Fluid / Q000737:chemistry*
chemical_list: D015415:Biomarkers; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12
keywords: CXC chemokine ligand–12; knee osteoarthritis; plasma; radiographic severity; synovial fluid