Laboratory test
Rheumatoid factor (RF)
Other names and abbreviations: RF, rheumatoid factor
Antibodies that often occur in rheumatoid arthritis.
A positive RF doesn't mean you have the disease – it can be present in healthy people, especially older ones. The doctor assesses it alongside symptoms and other tests (e.g. anti-CCP).
Typical ranges in adults
| Parameter | Typical range | What a deviation may mean |
|---|---|---|
| RF | usually below 14–20 IU/ml | depending on the laboratory method |
The ranges are approximate and differ between laboratories; they also depend on age, sex and pregnancy. A result outside the range doesn't always mean illness – discuss it with a doctor.
When it is done
With swelling and pain in several joints, morning stiffness.
How to prepare
Usually no special preparation is needed. In the morning before the blood draw, it's best not to eat a heavy breakfast – ask at reception.
