The rheumatoid factor test is used to help diagnose rheumatoid arthritis, and to distinguish it from other forms of arthritis.

The rheumatoid factor test also may be requested when a patient has symptoms suggesting Sjögren’s syndrome.

Symptoms may include an extremely dry mouth and eyes, and joint and muscle pain.

This test detects and measures rheumatoid factor, a type of autoantibody, in the blood.

rheumatoid factor may not directly cause joint damage,

but promote the body’s inflammation reaction which in turn contributes to autoimmune joint destruction. 

The RF test is sensitive but not very specific,

it can be found in diseases other than rheumatoid arthritis.  

It is most closely associated with rheumatoid arthritis.

but may also be present in other autoimmune disorders, such as Sjögren’s syndrome,

in some persistent bacterial and viral infections,

and can be found in a small but significant percentage of healthy people particularly in the elderly.

The RF test is not diagnostic or specific for RA or Sjögren’s syndrome.

It must be interpreted in conjunction with the patient’s symptoms and history,

and with tests of inflammation such as ESR or CRP.