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.
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.
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.
The CXCL12 levels in the plasma and SF may serve as effective biomarkers for the severity of OA.