What is being tested?
This test detects and measures rheumatoid factor (RF) in the blood. RF is an autoantibody, an IgM (immunoglobulin M) protein that is produced by the body’s immune system. Autoantibodies usually attack the patient’s own tissues, mistakenly identifying them as “foreign.” While the role of RF is not well understood, it is not thought to directly cause joint damage but to promote the body's inflammation reaction, which in turn contributes to autoimmune tissue destruction. The RF test is sensitive but nonspecific. It is most closely associated with rheumatoid arthritis (RA) but may also be present in a variety of other autoimmune disorders, such as Sjögren’s syndrome, in some persistent bacterial and viral infections, and it can be found in a small percentage of healthy people.

How is the sample collected for testing?
A blood sample is collected from a vein in your arm.