Rheumatoid Factor (RF)

Rheumatoid arthritis check

Rheumatoid factor (RF) is an antibody that the immune system can make against the body's own tissues. It is found in many people with rheumatoid arthritis, a long-term condition that causes painful, swollen and stiff joints. The test helps a doctor assess joint symptoms, but it is not a diagnosis on its own, because some people with rheumatoid arthritis test negative and some people without it test positive.

• To look into joint pain, swelling or morning stiffness, especially in the small joints of the hands and feet
• To help tell rheumatoid arthritis apart from other types of arthritis
• Alongside anti-CCP antibodies when rheumatoid arthritis is suspected
• To look into other autoimmune conditions, such as Sjögren's syndrome, which causes dry eyes and a dry mouth

You do not need to fast or change what you eat before this test. Keep taking your usual medicines, including painkillers, unless your doctor gives other advice. Wearing a loose sleeve makes the draw easier if your joints are stiff or sore.

Sample

Blood sample

How it works

The collector takes a small blood sample from a vein in your arm at home, so you do not need to travel while your joints are painful. The draw takes a few minutes, and you can rest your arm on a table or pillow if that is more comfortable.

Report

Within 24 hours of collection.

The report shows whether rheumatoid factor was found and, if so, the level compared with the laboratory's range. A positive result, especially a high level, supports rheumatoid arthritis when you also have typical joint symptoms. RF can also be positive in other autoimmune conditions, long-term infections such as hepatitis C, and some healthy people, particularly older adults. A negative result does not rule out rheumatoid arthritis, so your doctor will consider your symptoms, examination and other tests.

One test: Rheumatoid Factor (RF), from one blood sample.