What Is the Normal RA Factor Range?

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A normal rheumatoid factor is a result less than 40 to 60 units per milliliter, states MedlinePlus. The results of the rheumatoid factor test are sometimes reported as a titer, or the concentration of a certain substance. A normal rheumatoid factor titer is less than 1 to 80.

Rheumatoid factors are proteins that attack healthy tissue instead of harmful organisms, explains Mayo Clinic. Elevated RF levels commonly occur in people with autoimmune diseases, such as Sjogren’s syndrome and rheumatoid arthritis; however, some people with elevated RF levels are healthy, and some people with autoimmune diseases have normal RF levels.

Sarcoidosis, scleroderma, dermatomyositis and systemic lupus erythematosus can cause elevated RF levels, states MedlinePlus. Certain medical conditions also cause RF levels to rise. Viral infections, tuberculosis, chronic liver disease, parasitic infections and chronic lung disease are among the many potential causes of an elevated RF level.

A doctor usually orders the rheumatoid factor test when someone has the symptoms of rheumatoid arthritis, notes Lab Tests Online. Symptoms of RA include joint pain and swelling of the affected joints. Some people with RA also develop joint nodules. A doctor may order a CCP antibody test, complete blood count, erythrocyte sedimentation rate or antinuclear antibody test in conjunction with the RF test.