Rheumatoid Factor (RF), Serum/Plasma


Rheumatoid factors (RF) are IgM antibodies directed against the Fc (constant) region of the immunoglobulin G molecule. Rheumatoid factor is present in most people at very low levels, but higher levels are present in 5%-10% of the population, and this percentage rises with age. See Also Rheumatoid Factor (RF) Isotypes, Serum (see above) and Cyclic Citrullinated Peptide (CCP) Antibodies, Serum


Many rheumatologic and non-rheumatologic conditions such as rheumatoid arthritis, Sjögren’s syndrome, scleroderma, polymyositis and dermatomyositis, Systemic lupus erythematosus, mixed connective tissue disease, sarcoidosis, viral hepatitis, endocarditis, mycobacterial diseases, and syphilis can cause an elevated rheumatoid factor. In rheumatoid arthritis, only 60% of patients test positive for RF. High titres or levels may predict a more severe disease course.

Sample Type, Quantity & Conditions

1 ml Serum 1 ml Li-Heparin or K2-EDTA Plasma Stability: 24 Hours at 15-25 °C 3 Days at 2-8 °C 4 Weeks at (-15)-(-25) °C

Special Precautions

Freeze only once.

Normal Range

< 14 IU/mL

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