Table 2

Performance of the 12 investigated citrullinated peptides

Peptide

Percentage of RA sera reacting with the individual citrullinated peptides^a (%) 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 subtraction^b

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

ND^c

ND^c

ND^c

Peptides names are designated as in Table 1.

^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.

^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.

^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].

Hansson et al. Arthritis Research & Therapy 2012 14:R201   doi:10.1186/ar4039