WHICH ANTIGEN TO USE IN THE DETECTION OF RHEUMATOID FACTORS - COMPARISON OF PATIENTS WITH RHEUMATOID-ARTHRITIS AND SUBJECTS WITH FALSE POSITIVE RHEUMATOID-FACTOR REACTIONS

  • 1 September 1989
    • journal article
    • research article
    • Vol. 77  (3) , 349-355
Abstract
In the search for differences between rheumatoid factors (RF) in patients with rheumatoid arthritis (RA) and in non-rheumatoid subjects, the reactivity of IgM- and IgA-class RF with rabbit IgG (rIgG) and Fc fragments of rabbit and human IgG (rFc, hFc) was studied by enzyme immunoassay. From a community-based cohort (n = 7124) representing the adult population of Finland, RA patients (n = 130), other subjects positive in the Waaler-Rose (WaRo, sensitized sheep cell agglutination) test (n = 137), and controls matched for age, sex and living area were selected for further study. In Ra sera there was a good correlation between the results in the WaRo test and in the Igm-RF ELISA (rIgG, rFc and hFc). A considerable number of ''false positive'' sera, though positive in the WaRo test and the rIgG-ELISA, were negative in the rFc-ELISA. Twenty-two per cent of the false positive sera reacted with either hFc or rFC, both types being equally common. IgA-RF reacted more frequently with hFc than with rFc in both the RA and the ''false positive'' sera. In some sera, IgM- and IgA-RFs reacted differently with human and rabbit Fc, e.g. IgM-RF reacted only with human Fc, and IgA-RF reacted with both hFc and rFc, thus suggesting different regulation of their formation.