Rheumatoid Factor Blood Test
Feb 17, 2026
Rheumatoid Factor Blood Test
A rheumatoid factor (RF) blood test measures antibodies often present in rheumatoid arthritis (RA) and other autoimmune conditions—helping diagnose the cause of joint pain, swelling, and stiffness, particularly when it affects multiple joints symmetrically. About 80% of RA patients have positive RF, though it can also be positive in other conditions.
At Blood Test London, rheumatoid factor testing costs from £245 with results in 2-3 days.
Get Tested for Rheumatoid Factor
Understanding Rheumatoid Factor
RF is an antibody that attacks healthy tissue, particularly in joints. Its presence suggests autoimmune activity.
Results Interpretation
RF Level | Interpretation |
|---|---|
Negative (<14 IU/mL) | Normal |
Low positive (14-50) | Weak positive—may or may not indicate RA |
Moderate positive (50-100) | Suggestive of autoimmune condition |
High positive (>100) | Strong association with RA |
Conditions Associated with Positive RF
Rheumatoid arthritis (most common)
Sjögren's syndrome
Lupus (SLE)
Chronic infections
Hepatitis C
Some cancers
Healthy elderly (up to 10% have low positive RF)
Important Limitations
Not everyone with RA has positive RF (20% are "seronegative")
Positive RF doesn't always mean RA (can be positive in healthy people)
Diagnosis requires clinical assessment (symptoms, examination, imaging)
Usually tested with anti-CCP (more specific for RA)
When to Test
Joint pain and swelling (especially multiple joints)
Morning stiffness lasting >30 minutes
Symmetrical joint involvement
Family history of RA
Monitoring known RA
Related Tests
Test | Purpose |
|---|---|
Anti-CCP | More specific for RA |
ESR/CRP | Measure inflammation |
Full blood count | Check for anaemia of chronic disease |
X-rays/MRI | Assess joint damage |
Book Your Rheumatoid Factor Test
Price: From £245
Results: 2-3 days
Doctor review: A doctor always reviews every result
Fasting required: No
Phone: 020 3951 3429
Blood Test London by The Wellness. Rheumatoid factor testing from £245, results in 2-3 days.