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Definition

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 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.

How to Prepare for the Test

Most of the time, you do not need to take special steps before this test.

Normal Results

Results are usually reported in one of two ways:

  • Value, normal less than 15 IU/mL
  • Titer, normal less than 1:80 (1 to 80)

If the result is above the normal level, it is positive. A low number (negative result) most often means you do not have rheumatoid arthritis or Sjögren syndrome. However, some people who do have these conditions still have a negative 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:

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:

In some cases, people who are healthy and have no other medical problem will have a higher-than-normal RF level.

Why the Test is Performed

This test is most often used to help diagnose rheumatoid arthritis or Sjögren syndrome.

Review Date: 4/24/2017
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, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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