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Rheumatoid factor (RF)
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Rheumatoid factor (RF)

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Rheumatoid factor (RF) is a blood test that measures the amount of the RF antibody in the blood.

Most of the time blood is typically 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.

I Would Like to Learn About:

  • How the Test is Performed

    Most of the time blood is typically 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 Sjogren syndrome.

  • Normal Results

    Results are usually reported in one of two ways:

    • Less than 40-60 u/mL
    • Less than 1:80 (1 to 80) titer

    A low number (normal result) usually means you do not have rheumatoid arthritis or Sjogren syndrome. However, some people who do have these conditions still have a "normal" or low rheumatoid factor (RF).

    Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

  • What Abnormal Results Mean

    An abnormal result means the test is positive, which means higher levels of rheumatoid factor have been detected in your blood.

    • Most patients with rheumatoid arthritis or Sjogren 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 higher levels of rheumatoid factor has rheumatoid arthritis or Sjogren 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 rheumatoid factor:

    • Scleroderma
    • Systemic lupus erythematosus
    • Adult Still's disease
    • Dermatomyositis
    • Sarcoidosis

    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 problem will have a higher-than-normal RF level.

Related Information

  Rheumatoid arthrit...AntibodyDermatomyositisMononucleosisSclerodermaSystemic lupus ery...Adult Still's dise...Juvenile rheumatoi...Nephrotic syndrome...Sjögren syndrome...     Rheumatoid arthrit...SclerodermaSystemic lupus ery...

References

Andrade F, Darrah E, Rosen A. Autoantibiodies in rheumatoid arthritis. In: Firestein GS, Budd RC, Gabriel SE, et al, eds. Kelley's Textbook of Rheumatology. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2012:chap 56.

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Review Date: 4/20/2013  

Reviewed By: Gordon A. Starkebaum, MD, Professor of Medicine, Division of Rheumatology, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.

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