Rheumatoid factors are antibodies present in cases of rheumatoid arthritis, but also of Sjögren’s syndrome, scleroderma, dermatomyositis, Waldenström’s disease, sarcoidosis or even disseminated lupus erythematosus. Rheumatoid factors are generally used for the diagnosis of rheumatoid arthritis, and with anti-CCP antibodies, are the only biomarkers selected by the American Rheumatism Association for this pathology classification. These autoantibodies react with human IgGs. Rheumatoid factors are mostly class IgG antibodies, but rheumatoid factors of class IgA, IgD or even IgE are also found. Whatever their type, these antibodies are always directed to the Fc portion of human and animal IgGs.
The DiAgam reagent for the assay of rheumatoid factor detects IgG, IgA and IgM isotypes present in the sample.