Rheumatoid factor

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Also known as: RF
Formal name: Rheumatoid factor

At a Glance

Why Get Tested?

When to Get Tested?

If your doctor thinks that you have symptoms of RA or Sjögren’s syndrome

Sample Required?

A blood sample drawn from a vein in your arm

The Test Sample

What is being tested?

This test detects evidence of rheumatoid factor (RF), which is a type of autoantibody. An antibody is a protective protein that forms in the blood in response to a foreign material, known as an antigen (for example a bacterial protein). Autoantibodies, however, are antibodies that attack one's own proteins rather than foreign protein. Rheumatoid factors are autoantibodies directed against the class of immunoglobulins known as IgG and are members of a class of proteins that become elevated in states of inflammation.

Rheumatoid factor is elevated in many patients with both chronic and acute inflammation; it may be used to monitor the level of inflammation associated with rheumatoid arthritis (RA). Other markers such as CRP are considered more accurate for disease monitoring. Experts still do not understand exactly how RF is formed or why, but it is believed that RF probably does not directly cause joint damage but that it helps to promote the body's inflammation reaction, which contributes to the tissue destruction seen in rheumatoid arthritis.

How is the sample collected for testing?

A blood sample is collected from a vein in your arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.