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

  • IEA Hoffman1,

    Affiliated with

    • I Peene1,

      Affiliated with

      • A Union2,

        Affiliated with

        • L Meheus2,

          Affiliated with

          • T Huizinga3,

            Affiliated with

            • L Cebecauer4,

              Affiliated with

              • D Isenberg5,

                Affiliated with

                • K De Bosschere2,

                  Affiliated with

                  • F Hulstaert2,

                    Affiliated with

                    • EM Veys1 and

                      Affiliated with

                      • F De Keyser1

                        Affiliated with

                        Arthritis Res Ther20046(Suppl 1):16

                        DOI: 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

                         

                        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.

                        Authors’ Affiliations

                        (1)
                        Rheumatology, Ghent University Hospital
                        (2)
                        Innogenetics
                        (3)
                        Rheumatology, Leiden University Medical Center
                        (4)
                        Research Institute for Rheumatic Diseases
                        (5)
                        Rheumatology, University College London

                        Copyright

                        © BioMed Central Ltd 2004

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