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Table 2 Biomarker concentrations at baseline and follow-up in serum and synovial fluid after acute knee injury

From: Changes in serum and synovial fluid biomarkers after acute injury (NCT00332254)

  Synovial Fluid Levels Serum Levels Serum vs Synovial Fluid
Biomarker Baseline Mean ±SD Follow Up Mean ±SD P-value Baseline Mean ±SD Follow Up Mean ±SD P-value Mean Ratio (synovial fluid/serum levels) ± SD, P-value Correlation (between serum and synovial fluid levels), P-value
Inflammation markers
   IL-1β (pg/ml) 1.02 ± 0.66 0.61 ± 0.22 P = 0.124 0.17 ± 0.06 0.24 ± 0.12 P = 0.102 4.3 ± 2.1, p < 0.0001 rs = 0.358, P = 0.123
   CRP (μg/ml) 1.67 ± 1.28 0.68 ± 0.64 P = 0.039 3.18 ± 2.93 1.78 ± 2.10 P = 0.102 3.5 ± 4.2, p = 0.012 r s = 0.658, P = 0.002
Proteoglycan markers
   GAG (μg/ml) 330.7 ± 203.2 170.2 ± 45.9 P = 0.008 --- --- --- --- ---
   ARGS aggrecan (μg/ml) 230.7 ± 236.7 63.2 ± 54.0 P = 0.004 --- --- --- --- ---
   FA846 (ng/ml) 1134.0 ± 158.1 886.5 ± 295.8 P = 0.074 31.2 ± 35.1 32.4 ± 43.8 P = 0.520 59.1 ± 6.3, p = 0.0001 r s = -0.179, P = 0.464
   CS846 (ng/ml)* --- --- --- 72.3 ± 139.2 58.1 ± 131.6 P = 0.413 --- ---
Collagen markers
   C2C (ng/ml) 184.1 ± 37.6 208.9 ± 56.3 P = 0.301 226.5 ± 34.8 216.3 ± 49.2 P = 0.700 1.2 ± 0.5, p = 0.232 rs = -0.463, P = 0.046
   CTxII (μg/L) 0.59 ± 0.58 1.09 ± 0.63 P = 0.012 --- --- --- --- ---
   C1,2C (μg/ml) 0.28 ± 0.10 0.37 ± 0.08 P = 0.039 0.53 ± 0.18 0.51 ± 0.19 P = 0.638 1.8 ± 1.2, p = 0.005 rs = 0.209, P = 0.391
   CTxI (ng/ml) 0.75 ± 0.39 1.23 ± 0.67 P = 0.004 0.52 ± 0.32 0.66 ± 0.31 P = 0.083 1.6 ± 0.5, p = 0.0002 rs = 0.819, P < 0.0001
   NTx (nM BCE) 15.58 ± 4.37 19.64 ± 7.78 P = 0.008 18.67 ± 6.92 21.6 ± 4.2 P = 0.054 1.2 ± 0.2, p = 0.012 rs = 0.828, P < 0.0001
   CPII (ng/ml) 308.1 ± 257.4 318.3 ± 185.1 P = 0.820 365.2 ± 181.5 288.2 ±106.8 P = 0.102 1.3 ± 0.9, p = 0.976 rs = -0.102, P = 0.679
Osteocalcin (ng/ml) 15.43 ± 4.99 17.08 ± 6.16 P = 0.301 19.91 ± 8.54 16.3 ± 5.6 P = 0.032 1.2 ± 0.3, p = 0.012 rs = 0.747, P = 0.0002
Post-translational markers of protein age
   β-Aspartate (μM) 0.94 ± 0.32 0.76 ± 0.37 P = 0.129 --- --- --- --- ---
   D-Asx (D/D+L) 0.018 ± 0.001 0.019 ± 0.002 P = 0.423 --- --- --- --- ---
   D-Serine (D/D+L) 0.002 ± 0.001 0.003 ± 0.001 P = 0.055 --- --- --- --- ---
Other Biomarkers
   sCD44 (ng/ml)* 128.1 ± 49.0 105.0 ± 28.2 P = 0.250 115.9 ± 26.9 110.7 ± 39.0 P = 0.820 1.1 ± 0.4, p = 0.922 rs = 0.301, P = 0.226
   COMP (μg/ml) 140.9 ± 65.4 99.1 ± 32.3 P = 0.055 8.6 ± 4.1 8.0 ± 4.4 P = 0.278 21.2 ± 15.3, P = 0.0001 rs = -0.326, P = 0.173
   Tenascin C (ng/ml) 813.2 ± 428.6 908 ± 599 P = 0.570 --- --- --- --- ---
   Lubricin (nM equ) 390.4 ± 159.6 215.9 ± 59.0 P = 0.008 --- --- --- --- ---
   MMP-3 (ng/ml) 29.02 ± 20.84 30.89 ± 26.56 P = 0.910 0.05 ± 0.02 0.04 ± 0.02 P = 0.148 ↑738.8 ± 602.5, P = 0.0001 rs = 0.479, P = 0.038
  1. Results represent mean ± SD data for n = 9 patients for synovial fluid values and for serum n = 11 or n = 9 for * marked biomarkers due to sample depletion. Non-parametric paired analyses by Wilcoxon Signed Rank test were performed to evaluate for significant differences between baseline and follow up time points and between serum and synovial fluid values. Non parametric Spearman Rank correlations (r s ) were performed to determine correlations between synovial fluid and serum and the ratios reported are mean ratios ± SD.