Comparison and relevance of rheumatoid factors, antikeratin antibodies and anti-cyclic citrullinated peptides antibodies in rheumatoid arthritis

OBJECTIVES: to evaluate specificity and sensibility of the rheumatoid factors (RF), the anti-cyclic citrullinated peptide antibodies (CCP) and the anti-keratin antibodies (AKA) according to the rheumatoid arthritis (RA) diagnosis; pathology other than RA with at least one of these marker positive; the significance of the flocculent fluorescence of the antibodies AKA by indirect immunofluorescence (IIF). METHOD: two hundred forty height patients were studied: 121 RA, 89 inflammatory rheumatisms, 23 non inflammatory rheumatisms, and 15 non rheumatic affections. The RF was investigated by nephelometry, the anti-CCP by immunofluorometry and the AKA by IIF on rat oesophagus. RESULTS: specificity and sensibility were respectively in a retrospective manner: 68% and 83% for the RF, 95% and 76% for the anti- CCP, 83% and 40% for the AKA during RA with evolution of less than one year. The rates of agreements were: RF versus CCP: 81%, RF versus AKA: 57%, CCP versus AKA: 73%. Twelve patients with pathologies different from RA have positive anti-CCP or AKA. Thirty three of the patients with anti-CCP level superior to 130 U/mL have flocculent AKA versus only 5% when the anti-CCP are lower than 130 U/mL. CONCLUSION: the RF and the anti-CCP are complementary in RA. Autoimmune and neoplasic pathologies are sometimes responsible for the positivity of the anti-CCP and the AKA. The flocculent aspect of AKA in IIF may be associated with raised concentrations of anti-CCP.