Why it's done

A rheumatoid factor test is one of a group of blood tests primarily used to help pinpoint a diagnosis of rheumatoid arthritis. These other tests may include:

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

The amount of rheumatoid factor in your blood may also help your doctor choose the treatment approach that will work best for your situation.