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Rheumatoid factor (RF)

 

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

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

 

 

Open References

References

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

Mason JC. Rheumatic diseases and the cardiovascular system. In: Holcomb GW, Murphy JD, Ostlie DJ, eds. Ashcraft's Pediatric Surgery . 6th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 84.

 
  • Blood test

    Blood test - illustration

    Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.

    Blood test

    illustration

    • Blood test

      Blood test - illustration

      Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.

      Blood test

      illustration

    A Closer Look

     

      Self Care

       

        Tests for Rheumatoid factor (RF)

         
         

        Review Date: 4/28/2015

        Reviewed By: Gordon A. Starkebaum, MD, Professor of Medicine, Division of Rheumatology, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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