RF Test: Rheumatoid Factor Explained

Last updated: 12 December 2017

What is rheumatoid factor?

Rheumatoid factor (RF) is an autoantibody, a protein produced by the immune system that attacks healthy tissue, that is typically associated with rheumatoid arthritis and Sjogren’s syndrome.

What is a rheumatoid factor test?

Rheumatoid factor test is a blood test and is typically ordered by your doctor if you have symptoms of arthritis, such as painful, stiff, warm or swollen joints.

An RF test may also be a useful test when the diagnosis of Sjogren’s syndrome is being considered.

Sjogren’s syndrome symptoms include:

  • Dry mouth
  • Dry eyes
  • Aching joints and muscles
  • Can result in lung and kidney problems

Rheumatoid factor test results explained

The RF test result should not be considered in isolation, as it may be negative (normal) in people who have rheumatoid arthritis or Sjogren’s syndrome.

An RF test may also be falsely positive in many other conditions, including so-called connective tissue diseases, which often cause arthritis. The result needs to be interpreted in conjunction with a thorough medical assessment.

Approximately 90% of people with Sjogren’s syndrome and 80% of those with rheumatoid arthritis will become RF positive.

The rheumatoid factor can test negative in the first year or so of symptoms, and become positive later.

High levels of RF in patients with a clinical diagnosis of rheumatoid arthritis are associated with flare-ups in severity of the disease.

Related specialists

Related procedures

  • Blood Test (venesection)

Related tests

Also known as

  • RF

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This article is for informational purposes only and should not be taken as medical advice. If in doubt, HealthEngine recommends consulting with a registered health practitioner.