Autoimmunity
What is RF IgM?
The classic marker for rheumatoid arthritis
- Unit
- IE/mL
- Sample
- Serum
- Fasting
- No fasting needed
- Turnaround
- 2 days
Rheumatoid factor is the classic marker for rheumatoid arthritis. It is less specific than anti-CCP and can be positive in other autoimmune diseases.
Positive RF also appears in Sjögren's syndrome, chronic hepatitis, and in some healthy older people.
What does low RF IgM mean?
Negative RF makes RA less likely but does not rule out the disease.
What does high RF IgM mean?
Positive RF is interpreted alongside anti-CCP, joint symptoms, and the rest of the panel.
Panels that measure RF IgM
- Joint Pain Test
More markers in the same area
Launching in Stockholm in 2026.
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This is general information about the marker, not an assessment of your values and not medical advice. Last updated: August 2026.