Comparison between Anti-filaggrin, Anti-RA33 and Anti-Cyclic Citrullinated Peptide Antibodies in the Diagnosis of Rheumatoid Arthritis in Iraqi Patients

Abstract

Abstract Background: Anti-filaggrin, Anti-RA33 and anti-CCP antibodies are highly specific markers for rheumatoid arthritis (RA), but they are not detectable in all RA patients.Anti-filaggrin antibody are antibodies that reacts with keratinized tissue of animal esophagus(Anti-Keratin antibody) .Anti-RA33 antibodies are directed to the heterogeneous nuclear ribonucleoprotein A2 (hnRNP-A2),while anti-CCP antibodies are directed to modified epitope on proteins that undergo conversion of amino acid arginine to citrullin by citrullination.Objectives: The aim of this study was to show the correlation between anti-filaggrin antibodies, anti-RA33 antibodies, anti-CCP antibodies and rheumatoid factor (RF) in terms of sensitivity and specificity for the diagnosis of rheumatoid arthritis in Iraqi patients.Subjects and methods: This study was conducted in the period between April 2011 and October 2011 gathering 90 subjects. Fifty (50) of them were diagnosed as established RA patients and they were on treatment (the patients group) who were attending the rheumatology out patients clinic or admitted to Baghdad teaching hospital ,and forty (40) subjects were apparently without any arthritis (the control group). From each subject 5mls of venous blood was aspirated and centrifuged to separate the serum. The sera were stored at -20C and tested for anti-filaggrin antibodies, anti-RA33 antibodies, anti-CCP antibodies, and RF (IgM) antibodies using enzyme linked Immunosorbent assay (ELISA) kit.Results: There were forty two (42) seropositive patients (84.0%) and eight (8) seronegative patients (16.0%),with thirty four (34) (68.0 %) patients were anti-CCP antibodies positive and sixteen (16) (32.0%) patients were anti-CCP antibodies negative, while there were twenty nine (29)(58.0%) patients anti-RA33 antibodies positive and (21)(42.0%)patients were anti-RA33 antibodies negative. anti-filaggrin antibodies were positive in forty four (44) (88%) and it was negative only in six (6) (12%) patients. Conclusion: Anti-CCP antibodies have the highest specificity and anti-filaggrin antibodies have the highest sensitivity than anti-RA33 antibodies, but anti-RA33 antibodies are helpful in the diagnosis of patients who are anti-CCP negative and RF negative.Keywords: Rheumatoid arthritis, RA33 antibodies, anti-CCP antibodies anti-filaggrin antibodies.