ar1058 ARJ Meeting abstract <p>False positivity of rheumatoid factor and antibodies to citrullinated peptides in systemic lupus erythematosus</p> Hoffman IEA Peene I Union A Meheus L Huizinga T Cebecauer L Isenberg D Bosschere K De Hulstaert F Veys EM Keyser F De

Rheumatology, Ghent University Hospital, Gent, Belgium

Innogenetics, Gent, Belgium

Rheumatology, Leiden University Medical Center, Leiden, The Netherlands

Research Institute for Rheumatic Diseases, Piestany, Slovakia

Rheumatology, University College London, UK

 Arthritis Res Ther <p>24th European Workshop for Rheumatology Research</p> The organizer would like to thank the following companies who have generously supported the 24th European Workshop for Rheumatology Research: Abbott Immunology (Main sponsor), Amgen, Aventis, Bristol Myers Squibb, Schering Plough, Roche, MSD, Novartis, Wyeth Meeting abstracts <p>24th European Workshop for Rheumatology Research</p> Berlin, Germany 26–29 February 2004 1478-6354 2004 6 Suppl 1 16 10.1186/ar1058 16 1 2004 24 2 2004

Background

Rheumatoid factor (RF) is found in patients with systemic lupus erythematosus (SLE). Anti-citrullinated peptide antibodies (ACPA) are more specific for rheumatoid arthritis than RF.

Objective

Our aim was to determine the prevalence of RF and ACPA in SLE patients.

Methods

In this study, samples from 201 consecutive patients diagnosed with SLE and fulfilling ACR criteria were used. Fine ANA reactivities were tested by INNO-LIA™ ANA (Innogenetics, Gent, Belgium) and by IIF on C. luciliae. RF was detected by latex fixation. ACPA were detected by anti-CCP2 ELISA (Euro-Diagnostica, Arnhem, The Netherlands) and by a research INNO-LIA™ RA (Innogenetics, Gent, Belgium) for the detection of anti-pepA and anti-pepB antibodies. The prevalences of ACPAwere compared by the McNemar test.

Results

RF at a titre ≥160 was found in 26 patients (13.0%). ACPA were found in 16 samples (Table 1). The prevalence of anti-CCP2 antibodies was significantly higher than that of anti-pepA antibodies (P = 0.001) and anti-pepB antibodies (P = 0.022).

<p>Table 1</p>

Characteristics of ACPA-positive SLE patients

RF (titre)

Anti-CCP2 (U/ml; cut-off 25 U/ml)

Anti-pepA

Anti-pepB

ANA fine reactivities

1

1280

186

+

+

Ro60, SSB

2

0

28

-

-

SmB, SmD, histones, dsDNA

3

640

9

-

+

RNP-C

4

0

168

-

-

dsDNA

5

0

53

-

-

SmB, dsDNA

6

80

2

-

+

Histones, dsDNA

7

0

76

-

-

SmB, RNP-A, RNP-C, RiboP, histones

8

40

64

-

-

SmD, SmB, RNP-70k, RNP-C, RiboP

9

0

58

-

-

-

10

320

110

-

-

SmB, RNP-70k, RNP-A, RNP-C, Histones, dsDNA

11

0

28

-

-

-

12

0

36

-

-

-

13

320

78

+

+

SmB, RNP-70k, RNP-A, RNP-C

14

80

56

-

-

RNP-A, RiboP, Histones

15

640

52

-

-

RNP-70k, RNP-A

16

320

1600

+

+

Ro60

Conclusion

RF is found in 13.0% of SLE patients. Anti-CCP2 antibodies are false-positive in 7.0% (n = 14) of SLE patients, which occurs significantly more often than anti-pepA (1.5%, n = 3) and anti-pepB (2.5%, n = 5) antibodies.