Rheumatoid factor (RF) is a blood test that measures the amount of the RF antibody in the blood. A rheumatoid factor (RF) test measures the amount of rheumatoid factor (RF) in your blood. Rheumatoid factors are proteins produced by the immune system. Normally, the immune system attacks disease-causing substances like viruses and bacteria.
How the Test is Performed
Most of the time, blood is drawn from a vein located on the inside of the elbow or the back of the hand.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin.
- The blood collects in a small glass tube called a pipette, or onto a slide or test strip.
- A bandage is put over the spot to stop any bleeding.
How to Prepare for the Test
Most of the time, you do not need to take special steps before this test.
How the Test will Feel
You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.
Why the Test is Performed
This test is most often used to help diagnose rheumatoid arthritis or Sjögren syndrome.
Normal Results
Results are usually reported in 1 of 2 ways:
- Less than 40 to 60 u/mL
- Less than 1:80 (1 to 80) titer
A low number (normal result) most often means you do not have rheumatoid arthritis or Sjögren syndrome. However, some people who do have these conditions still have a “normal” or low RF.
Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.
What Abnormal Results Mean
An abnormal result means the test is positive, which means a higher level of rheumatoid factor has been detected in your blood.
- Most people with rheumatoid arthritis or Sjögren syndrome have positive RF tests.
- The higher the level, the more likely one of these conditions is present. There are also other tests for these disorders that help make the diagnosis.
- Not everyone with a higher level of RF has rheumatoid arthritis or Sjögren syndrome.
Your provider may do another blood test (anti-CCP antibody), to help diagnose rheumatoid arthritis.
People with the following diseases may also have higher levels of RF:
- Systemic lupus erythematosus
- Dermatomyositis and polymyositis
- Sarcoidosis
- Mixed cryoglobulinemia
- Mixed connective tissue disease
Higher-than-normal levels of RF may be seen in people with other medical problems. However, these higher RF levels cannot be used to diagnose these other conditions:
- AIDS, hepatitis, influenza, infectious mononucleosis, and other viral infections
- Certain kidney diseases
- Endocarditis, tuberculosis, and other bacterial infections
- Parasite infections
- Leukemia, multiple myeloma, and other cancers
- Chronic lung disease
- Chronic liver disease
In some cases, people who are healthy and have no other medical problems will have a higher-than-normal RF level.
FAQ
What is a normal RF factor?
- The normal range of RF is from 0-20 IU/ml. RF above 20 IU/ml is not considered enough to diagnose RA, as there are other reasons the RF level may be elevated.
What does it mean if your RF factor is high?
- A positive rheumatoid factor test result indicates that a high level of a rheumatoid factor was detected in your blood. A higher level of rheumatoid factor in your blood is closely associated with autoimmune disease, particularly rheumatoid arthritis.
Is rheumatoid arthritis RF positive?
- An abnormal result means the test is positive, which means a higher level of RF has been detected in your blood. Many people with rheumatoid arthritis or Sjögren syndrome have positive RF tests. The higher the level, the more likely one of these conditions is present.
Is rheumatoid factor 10 normal?
- Most medical centers consider the normal range of rheumatoid factors to be up to 10 IU/mL or 20 IU/mL, says rheumatologist Steffan Schulz, MD, assistant professor of clinical medicine with Penn Medicine in Philadelphia.
What are the normal ranges for rheumatoid factors?
- The “normal” range (or negative test result) for rheumatoid factor is less than 14 IU/ml. Any result with values of 14 IU/ml or above is considered abnormally high, elevated, or positive.
What is considered a positive rheumatoid factor?
- Reference ranges may vary, but normally values >20 IU/ml are considered positive; however, most RA patients have values >160 IU. As with the rheumatoid factors, values >20 are normally considered positive; however, most RA patients will have strong positive results (i.e., >60 units).
Is rheumatoid factor positive in lupus?
- Rheumatoid factor (RF) is found commonly in patients with systemic lupus erythematosus (SLE), and has been associated with a more benign disease course. Anti-citrullinated peptide antibodies (ACPA) are more specific for rheumatoid arthritis (RA).
Can you have a positive rheumatoid factor and not have rheumatoid arthritis?
- Rheumatoid factors are proteins that the immune system produces when it attacks healthy tissue. About half of all people with rheumatoid arthritis have high levels of rheumatoid factors in their blood when the disease starts, but about 1 in 20 people without rheumatoid arthritis also test positive.
How do I lower my rheumatoid factor?
Lifestyle and home remedies
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