Rheumatoid factor R.F detection and significance

What is Rheumatoid factor (R.F) ?

• It is an IgM Ab (occasionally IgG, IgA or IgE) which reacts with Fc portion of human IgG, this occurs usually in patients with rheumatoid
disease (70-80% of cases), but is not diagnostic.
• It exists as an (Rh.F. - Ig.G - C) complex in synovial membrane.
So, complement is lowered in synovial fluid and not in the serum.

Methods of detection


1- Latex method (agglutination test)

Ab (Rh. F. in the serum) +
Ag (latex coated with Ig G)

2- Rose waaler test. (agglutination test)
Ab (Rh. F. in the serum) +
Ag (sheep's RBCs coated witl1 anti-erythrocyte antibodies)

Latex is more sensitive, but Rose Waaler is more specific.

Conditions in which Rh. F is +ve

Autoimmune rheumatic diseases .
 - Rheumatoid arthritis (70 % - 80 %).
 - SLE (15-35 %)
 - Polymyositis, dermatomyositis (5-10 %).
 - Mixed connective tissue disease (50-60%).
 - Sjogren's disease (90 %).
 - Scleroderma (30 %).

Infections
 - T. B.           - Infective endocarditis.
 - Syphilis       - Kala - azar
 - HCV - HIV

Normal population
Especially elderly and relatives of patients with rheumatoid arthritis.

Miscellaneous .
Autoimmune hepatitis.        - Fibrosing alveolitis.
Sarcoidosis.                       - Waldenstroms macroglobulmamia.
Chronic liver disease.         - Cryoglobulinemia.

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