Autoimmune serology
Rheumatoid factorRF
IgM autoantibody against IgG Fc; sensitive but not specific for RA.
Sample
Serum
Clinical reference range
— to 14 IU/mL
Negative
Conv: —–14 IU/mL
Biology
What it measures
IgM (less commonly IgA/IgG) directed against the Fc portion of IgG.
Differential
Causes of abnormal values
Causes of HIGH
- ↑Rheumatoid arthritis
- ↑Sjögren syndrome
- ↑Cryoglobulinemia (HCV)
- ↑Endocarditis
- ↑Aging (5–10% >65 y)
Related