False positivity of rheumatoid factor and antibodies to citrullinated peptides in systemic lupus erythematosus

IEA Hoffman¹, I Peene¹, A Union², L Meheus², T Huizinga³, L Cebecauer⁴, D Isenberg⁵, K De Bosschere², F Hulstaert², EM Veys¹ and F De Keyser¹

¹Rheumatology, Ghent University Hospital, Gent, Belgium

²Innogenetics, Gent, Belgium

³Rheumatology, Leiden University Medical Center, Leiden, The Netherlands

⁴Research Institute for Rheumatic Diseases, Piestany, Slovakia

⁵Rheumatology, University College London, UK

from 24th European Workshop for Rheumatology Research
Berlin, Germany. 26–29 February 2004

Arthritis Res Ther 2004, 6(Suppl 1):16doi:10.1186/ar1058

Received:	16 January 2004
Published:	24 February 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).

Table 1. Characteristics of ACPA-positive SLE patients

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.

This article is part of the supplement: 24th European Workshop for Rheumatology Research