Back Blood-tests Explained


Rheumatoid Factor


At a Glance

Why Get Tested?

To help diagnose rheumatoid arthritis (RA)

When to Get Tested?

When you have joint pain and fatigue that your health care provider suspects may be due to RA

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Rheumatoid factor (RF) is an autoantibody, an immunoglobulin M (IgM) protein that is produced by the body's immune system. Autoantibodies attack aperson's own tissues, mistakenly identifying the tissue as "foreign." While the biologic role of RF is not well understood, its presence is useful as an indicator of inflammatory and autoimmune activity. This test detects and measures RF in the blood.

The RF test is a valuable test for helping to diagnose rheumatoid arthritis (RA). About 80% of those with RA will have a positive RF test.However, RF may also be detected in people with a variety of other disorders, including other autoimmune disorders such as Sjögren syndrome, as well as persistent bacterial, viral, and parasitic infections, and certain cancers.It may sometimes be seen in those with lung disease, liver disease, and kidney disease, and it can be found in a small percentage (1-5%) of healthy people.

How is the sample collected for testing?

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

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

No test preparation is needed.

The Test



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