Rheumatoid Factor

Also written as: RF

An antibody often present in rheumatoid arthritis, though it also appears in many other settings.

What it measures

The level of rheumatoid factor, an antibody that targets the body's own antibodies. Despite the name, it is not exclusive to rheumatoid arthritis and can appear in a range of other situations, including in healthy people.

Why a doctor orders it

Usually ordered when joint pain, morning stiffness, or joint swelling raises the question of rheumatoid arthritis or another inflammatory joint condition. It is often paired with anti-CCP antibodies, which are more specific for rheumatoid arthritis.

What is generally associated with a higher result

Broadly associated with rheumatoid arthritis, but also with Sjogren's syndrome, chronic infections such as hepatitis, and other inflammatory conditions. It is also found in a portion of healthy people, and this becomes more common with age.

What is generally associated with a lower result

A negative result is generally the expected finding. Some people with rheumatoid arthritis test negative, which is why the test is always read alongside symptoms and other markers rather than on its own.

Everyday things that move this number

Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:

Age - positivity becomes more common in healthy older adults
Recent or lingering infections, including common viral illnesses
Smoking
Recent vaccinations, which can cause a temporary rise

Questions to take to your appointment

Should anti-CCP antibodies be checked as well, since they are more specific?
Could a recent infection or vaccination explain a positive result?
Do my joint symptoms fit a pattern that this result supports or argues against?

Build a printable questionnaire with your own results →

Where to read more

MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .

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