Description

A rheumatoid factor (RF) test measures the level of rheumatoid factor in your blood to help diagnose rheumatoid arthritis (RA) and other conditions. 

Purpose

Diagnose RA

  • The RF test is a key part of diagnosing RA, an inflammatory condition that causes joint pain, swelling, and stiffness. 

Diagnose other conditions

  • The RF test can help diagnose other autoimmune diseases, chronic infections, and some cancers. 

Determine severity

  • The RF test can help determine how severe RA is and if it's likely to affect organs. 

Determine treatment

  • The RF test can help determine the best treatment for RA and other conditions. 

What is rheumatoid factor? 

  • Rheumatoid factor is an autoantibody that attacks your body's own proteins.
  • RF levels increase in response to inflammation caused by RA.

Other tests for RA 

  • Anti-nuclear antibody (ANA)
  • Anti-cyclic citrullinated peptide (anti-CCP) antibodies
  • C-reactive protein (CRP)
  • Erythrocyte sedimentation rate (ESR, or sed rate)

Fasting not required.