Blood draw
Rheumatoid Factor
Rheumatoid Factor (RF) for suspected rheumatoid arthritis.
€ 60,00
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Inflammation and immunity · Blood
Rheumatoid factor
Antibodies found in rheumatism and Sjögren's syndrome, but also in healthy people and in other diseases.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
Rheumatoid factor: what is measured?
Rheumatoid factors are autoantibodies directed against the body's own immune protein IgG. They are usually of the IgM type. This test measures the amount of rheumatoid factor in the blood, without distinguishing between types. Rheumatoid factors do not damage the joints directly, but they are part of inflammation that can do so over time.
What can it detect?
- Rheumatoid arthritis (RA), a chronic joint inflammation caused by the body's own immune system
- Sjögren's syndrome (chronic inflammation of the tear and salivary glands)
- Long-lasting infections and other inflammatory diseases in which rheumatoid factor develops as a side effect
Result
What does the result mean?
Rheumatoid factor too high
A raised rheumatoid factor fits rheumatoid arthritis or Sjögren's syndrome if you also have symptoms of these, such as inflamed and stiff joints or a dry mouth and dry eyes. The higher the value, the greater the chance of RA. The test is not very specific: a raised value also occurs in healthy people, more often at older ages, and in long-lasting infections such as endocarditis (inflammation of the heart valves), tuberculosis or syphilis, in sarcoidosis and in diseases of the lungs, liver or kidneys. Without matching symptoms, a raised value therefore says little.
Rheumatoid factor too low
A low or undetectable rheumatoid factor is the normal result. It does not rule out rheumatoid arthritis: in about 1 in 5 people with RA the test is negative, and in Sjögren's syndrome even more often. The diagnosis rests mainly on the symptoms and the examination of the joints; anti-CCP is the more specific blood test for this.
After an abnormal result
With inflamed joints, the GP usually refers you to a rheumatologist, even if the rheumatoid factor is normal. The rheumatologist assesses the result together with anti-CCP, the physical examination and the inflammation markers. A raised rheumatoid factor without symptoms usually does not lead to further tests.
Reliability
How reliable is the test?
Rheumatoid factor is an old, widely used test, but less specific than anti-CCP. When RA is suspected, anti-CCP tells you the most; rheumatoid factor is an addition to it. When the chance of RA is small, or in people without joint symptoms, both tests say little. The Dutch guideline on rheumatoid arthritis points out that rheumatoid factor in particular gives relatively many false-positive results. The test is not suitable for monitoring disease activity.
What can affect the result?
- Rheumatoid factor also occurs in healthy people, more often at older ages, and in long-lasting infections and other inflammatory diseases.
- Up to 5 in 100 healthy people have rheumatoid factor and/or anti-CCP without rheumatoid arthritis.
- Measurement methods and reference values differ greatly between laboratories; results from different labs are not easy to compare.
- The level of the value does not always match the severity of the symptoms.
Who it is for
Who is the test useful for?
Useful for
The result says the most with inflamed, stiff joints where a doctor is thinking of rheumatoid arthritis, preferably together with anti-CCP, and with dry eyes and a dry mouth plus joint symptoms where Sjögren's syndrome is being considered. With joint pain without signs of inflammation, with general tiredness or in people without symptoms, a positive result says little, because it is then usually not caused by a rheumatic disease.
How common is it?
Rheumatoid arthritis affects about 0.5 to 1 in 100 people; each year about 3 in 10,000 people are diagnosed with it. Sjögren's syndrome is rarer. A raised rheumatoid factor is more common than these diseases: up to 5 in 100 healthy people have rheumatoid factor and/or anti-CCP, and in older people a positive result without disease is found more often.
NVKC Zinnige Diagnostiek and FMS guideline on rheumatoid arthritis (NVR)
Drawbacks and risks
- A raised rheumatoid factor without symptoms is often not caused by rheumatism and can lead to unnecessary worry or referral, especially in older people.
- A normal result can give false reassurance when joints are in fact inflamed.
Get tested
Rheumatoid factor: test panels
Rheumatoid factor is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and resultsMore explanations
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