Serum RA Factor

Specimen Required

3-5cc Clotted Blood or Serum

Fasting Required

Purpose of the Test

To help diagnose rheumatoid arthritis (RA) and Sjögren’s syndrome

When this test is required

The test for RF may be requested when a patient has signs of RA and these have persisted for more than 6 weeks. Symptoms may include pain, warmth, swelling, and morning stiffness in the joints, nodules under the skin, and, if the disease has progressed, evidence on X-rays of swollen joint capsules and loss of cartilage and bone. An RF test may be repeated when the first test is negative and symptoms persist. The RF test also may be requested when a patient has symptoms suggesting Sjögren’s syndrome. Symptoms may include an extremely dry mouth and eyes, and joint and muscle pain. Symptoms may also be mixed as patients may have more than one autoimmune disorder. Sjogren’s syndrome can occur by itself or following RA, or systemic lupus eryhtematosus (SLE). Patients with RA and/or Sjogren’s syndrome may also have other autoimmune disease such as thyroid disorders.

What the Test Detects

This test detects and measures rheumatoid factor (RF), a type of “autoantibody”, in the blood. We all have antibodies (also known as immunoglobulins) in our blood, which are protective proteins which defend the body against infection, particularly from bacteria. However, “autoantibodies” may attack the patient’s own tissues mistakenly identifying them as “foreign”. While the role of RF is not well understood, it may not directly…This test detects and measures rheumatoid factor (RF), a type of “autoantibody”, in the blood. We all have antibodies (also known as immunoglobulins) in our blood, which are protective proteins which defend the body against infection, particularly from bacteria. However, “autoantibodies” may attack the patient’s own tissues mistakenly identifying them as “foreign”. While the role of RF is not well understood, it may not directly cause joint damage, but promote the body’s inflammation reaction which in turn contributes to autoimmune joint destruction. The RF test is sensitive but not very specific, it can be found in diseases other than rheumatoid arthritis (RA). It is most closely associated with RA but may also be present in other autoimmune disorders, such as Sjögren’s syndrome, in some persistent bacterial and viral infections, and can be found in a small but significant percentage of healthy people particularly in the elderly. 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? None required See MoreSee Less

Preparation for the Test

None required

Sample Requirements

A blood sample taken from a vein in your arm

Additional Notes

The RF test is not diagnostic or specific for RA or Sjögren’s syndrome. It must be interpreted in conjunction with the patient’s symptoms and history, and with tests of inflammation such as ESR or CRP. The frequency of falsely positive RF results increases with as we get older.

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