Rheumatoid factor

Other names: RF

Rheumatoid factor is a form of antibody, known as an autoantibody. Unlike normal antibodies, which protect the body against infections and illness, autoantibodies attack the body because they identify the tissue as foreign. The presence of rheumatoid factor may result in joint pain and damage because it may provoke the body’s inflammation reaction.

Why is the test used?

The test is primarily used to diagnose rheumatoid arthritis but it may also be involved in the diagnosis of Sjogren’s syndrome (this is an autoimmune condition, which affects the secretion of mucus, causing symptoms such as dry mouth, joint pain and fatigue).

The test is usually ordered when a doctor suspects that a patient has got either rheumatoid arthritis or Sjogren’s syndrome; symptoms of rheumatoid arthritis include pain, swelling in the joints, stiff joints (particularly in the morning) and, in advanced cases, swollen joint capsules and bone loss.

How is the test done?

The test is done by taking and analysing a sample of blood; a needle is inserted into a vein in the arm and the blood is drawn out and collected in a syringe. Once the doctor or nurse has a sufficient sample, the blood will be bottled, labelled and sent off to the laboratory for evaluation.

What do the test results mean?

If concentrations of rheumatoid factor are high and the patient has symptoms of rheumatoid arthritis, it is highly likely that the patient has rheumatoid arthritis.

If a patient has high levels of RF and symptoms of Sjogren’s syndrome, this may indicate that they have the syndrome; however, this is not always the case so further tests will usually be ordered.

Positive RF tests may be seen in healthy patients or patients with infections, cancer, liver and kidney disease, tuberculosis and sarcoidosis.

As the test is not very specific, the test results alone cannot be used to reach a diagnosis; further tests will almost always be ordered and the results of the test will be considered alongside other factors, including the patient’s symptoms and medical history.

Specific Blood Tests

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