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Table 2 Performance of the 12 investigated citrullinated peptides

From: Validation of a multiplex chip-based assay for the detection of autoantibodies against citrullinated peptides

Peptide Percentage of RA sera reacting with the individual citrullinated peptidesa (%) at 98.0% specificity Number of positive patients/number of CCP2-positive patients (%)a Percentage of RA sera reacting with the individual citrullinated peptides (%) at 98.0% specificity after arginine subtractionb Number of positive patients/number of CCP2-positive patients (%)b after arginine subtraction Positive (+) or negative (-) effect of arginine subtraction on the diagnostic performance
Eno5-21 (CEP-1) 39.4 91.0 40.9 94.5 +
Vim60-75 31.9 73.7 40.0 92.4 +
Vim2-17 10.8 24.9 8.0 18.5 -
Fil307-324 (CCP1) 32.8 75.8 32.5 75.1 -
Fibβ36-52 45.2 104.4 41.9 96.8 -
Fibβ563-583 31.0 71.6 31.5 72.7 +
Fibβ580-600 10.5 24.2 9.8 22.6 -
Fibβ62-81a 19.8 45.7 20.6 47.6 +
Fibβ62-81b 28.0 64.7 26.1 60.3 -
Fibβ60-74 38.8 89.6 37.3 86.1 -
Fibα621-635 25.9 59.8 29.0 67.0 +
CII 359-369 (CitC1) 18.8 43.4 NDc NDc NDc
  1. Peptides names are designated as in Table 1.
  2. aThese percentages should be compared with the fact that 43.3% of all RA patients in the present selection of EIRA patients were anti-CCP2 positive.
  3. bFluorescence intensities for the arginine control peptides were subtracted from the fluorescence intensities for each measurement among RA patients and controls, whereupon the performance was calculated on the net values.
  4. cNo subtraction was done for this peptide as the arginine control peptide is itself an autoantigen with conformational epitopes that are destroyed by citrullination [20].