Rheumatoid factor (RF) is an autoantibody that targets the body’s own tissues.

Elevated RF levels are strongly associated with rheumatoid arthritis (RA), though they may also be seen in other autoimmune or chronic inflammatory diseases.

Clinical uses include:

Supporting the diagnosis of rheumatoid arthritis.

Differentiating autoimmune disorders such as Sjögren’s syndrome or systemic lupus erythematosus (SLE).

Monitoring disease progression and treatment response in RA patients.

The test is performed using a blood sample.

Analyte: Rheumatoid factor antibodies in serum.

Normal Range: < 20 IU/mL (varies slightly by lab).

Abnormal Findings:

High RF: Suggests rheumatoid arthritis, Sjögren’s syndrome, lupus, chronic infections, or certain cancers.

Low/negative RF: Does not rule out RA, as some patients may be seronegative.

Clinical Use:

Provides supportive evidence for autoimmune disease diagnosis.

Helps distinguish RA from other causes of joint pain.

Often interpreted alongside anti-CCP antibody test for greater diagnostic accuracy.