Immune & Inflammation
Rheumatoid Factor (RF)
Immune & Inflammation
Autoantibody associated with rheumatoid arthritis and other autoimmune conditions.
VAT-exempt medical service
Here's something your immune system would rather you didn't know: sometimes it gets confused. Rheumatoid factor (RF) is an autoantibody — a protein made by your own immune system that mistakenly targets your own healthy tissue. When RF shows up, it signals inflammatory and autoimmune activity. It's found in 70-90% of people with rheumatoid arthritis, making it an important (though not perfect) piece of the diagnostic puzzle.
If your joints are painful, warm, swollen or stiff — especially in the morning — it's worth checking RF. Same goes if you have a family history of rheumatoid arthritis or an existing autoimmune condition. And if your first test came back negative but your joints are still grumbling? Test again. RF can take time to show up.
What a high value can mean
A positive RF test means autoantibodies are present. In people showing clinical signs of RA, significant RF levels indicate a high likelihood of the disease. Studies show that elevated RF in the general population is linked to up to a 26-fold higher long-term risk of developing RA. But RF alone doesn't seal the deal — it needs to be interpreted alongside your symptoms and other tests.
What a low value can mean
A negative RF means no rheumatoid factor antibodies were found. However, roughly 20% of RA patients have no detectable RF. A CCP antibody test can fill in the gaps. Bottom line: RA is a clinical diagnosis that looks at the whole picture — symptoms, history and multiple lab findings.
No prep needed. Bring valid ID to your appointment.
Order your test
Choose your test and pay online. Your lab referral is created straight away.
Give your sample
Visit any of our partner sampling locations. No appointment needed at most of them.
The lab analyses it
Your sample is analysed at an accredited Swedish laboratory.
Get your results
Your values appear in your account with reference ranges and an explanation of each marker.
Yes. About 20% of RA patients are 'seronegative' — they have RA without detectable RF. A CCP antibody test can help confirm or rule out RA in these cases. Ultimately, the diagnosis is based on the full clinical picture.
Nope. RF can also pop up in other autoimmune conditions like Sjogren's syndrome, lupus and hepatitis C, as well as in some perfectly healthy people — especially at low levels or with age.