A rheumatoid factor test measures the amount of rheumatoid factor in your blood. Rheumatoid factors are proteins produced by your immune system that can attack healthy tissue in your body.
High levels of rheumatoid factor in the blood are most often associated with autoimmune diseases, such as rheumatoid arthritis and Sjogren’s syndrome. But rheumatoid factor may be detected in some healthy people, and people with autoimmune diseases sometimes have normal levels of rheumatoid factor.
What is rheumatoid factor (RF)?
Rheumatoid factor (RF) is a protein made by your immune system that can attack healthy tissue in your body. Healthy people don’t make RF. So, the presence of RF in your blood can indicate that you have an autoimmune disease.
Sometimes people without any medical problems produce a small amount of RF. That’s very rare, and doctors don’t fully understand why it happens.
Why do RA Factor test?
Your doctor may order a blood test to check for the presence of RF if they suspect you have an autoimmune condition, such as rheumatoid arthritis or Sjogren’s syndrome. Other health problems that can cause higher-than-normal levels of RF to include:
- chronic infection
- cirrhosis, which is scarring of the liver
- cryoglobulinemia, which means there are or abnormal proteins in the blood
- dermatomyositis, which is an inflammatory muscle disease
- inflammatory lung disease
- mixed connective tissue disease
Some health problems may cause elevated RF levels, but the presence of this protein alone is not used to diagnose these conditions. These illnesses include:
Symptoms to do RA Factor test?
Doctors commonly order this test for people who have symptoms of rheumatoid arthritis, which include:
- joint stiffness
- increased joint pain and stiffness in the morning
- nodules under the skin
- a loss of cartilage
- bone loss
- warmth and swelling of the joints
Your doctor may also order tests to diagnose Sjogren’s syndrome, a condition in which your white blood cells attack the mucous membranes and moisture-secreting glands of your eyes and mouth.
The symptoms of this chronic autoimmune condition are primarily dry mouth and eyes, but they can also include extreme fatigue and joint and muscle pain.
Sjogren’s syndrome primarily occurs in women and sometimes appears with other autoimmune conditions, including rheumatoid arthritis.
What is the normal range for rheumatoid factor?
The “normal” range (or negative test result) for rheumatoid factor is less than 15 IU/ml. Any result with values 15 IU/ml or above is considered abnormally high, elevated, or positive.
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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)
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