Rheumatoid Factor (RF) is an autoantibody directed against the Fc portion of IgG.

The quantitative test provides an exact measurement of RF levels in blood serum.

Clinical uses include:

Supporting diagnosis of rheumatoid arthritis (RA).

Detecting other autoimmune diseases (e.g., Sjögren’s syndrome, lupus).

Differentiating inflammatory arthritis from non-inflammatory joint conditions.

Monitoring disease progression and treatment response in RA patients.

The test is performed using a blood sample, typically via nephelometry or ELISA methods.

Analyte: Rheumatoid Factor (RF) concentration in blood serum.

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

Elevated Levels:

Suggestive of rheumatoid arthritis (though not specific).

May also be seen in other autoimmune diseases, chronic infections, or even in healthy individuals (especially elderly).

Clinical Use:

Provides quantitative measurement of RF for diagnostic accuracy.

Helps assess severity and prognosis of RA.

Guides further confirmatory tests (e.g., anti-CCP antibodies).