RA Factor Test: Understanding Rheumatoid Arthritis Diagnosis

The RA factor test is used predominately to help evaluate if you have rheumatoid arthritis. Also called the RF test, it checks for factors in your blood caused by rheumatoid arthritis, which is an autoimmune disease.

Procedure

• The RA test is performed by a member of a medical staff, who will take a sample of your blood.

Diagnosis

• Dr. Joel Kremer, of Albany Medical College, states that tests for rheumatoid arthritis are only indications. Diagnosis depends on several factors, including symptoms, family history and a physical exam.

Laboratory

• The blood is examined for rheumatoid factors. Laboratories may use nephelometric or agglutination methods to find and measure these factors.

Positive

• A positive result may indicate rheumatoid arthritis, other autoimmune diseases, or many other disorders. However, approximately four percent of healthy people, especially the elderly, have positive results.

Normal

• Using the nephelometric method, a normal value is under 50 u/mL. Using the agglutination method, a normal result is under 1:80 titer. A normal result does not mean you don't have rheumatoid arthritis, since almost 20 percent of people with rheumatoid arthritis do not have RA factors.