Rheumatoid Factor (IgM) by Immunoassay (Serum/Plasma)
This test measures the presence of rheumatoid factor, an antibody found in the blood of some people with rheumatoid arthritis or other autoimmune conditions.
["Rheumatoid factor helps identify possible autoimmune diseases like rheumatoid arthritis."]
Key facts at a glance
- LOINC
- 5299-3
- Short code
- Rheumatoid fact Titr Ser LA
- Synonyms
- Rheumatoid fact Titr Ser LA
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- la
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What Is Rheumatoid Factor?
Rheumatoid factor is an antibody that can attack healthy cells in your body. While it’s common in people with rheumatoid arthritis, it can also appear in other autoimmune diseases or certain infections. This test checks for its presence in your blood to help diagnose or monitor these conditions.
Why Might You Need This Test?
Your doctor may order this test if you have symptoms like joint pain, swelling, or stiffness, or if you have a family history of autoimmune diseases. It can also be used to monitor disease activity in people already diagnosed with rheumatoid arthritis or other conditions linked to rheumatoid factor.
What to Expect During the Test
A blood sample is taken from a vein in your arm. You may feel a small pinch, but it usually doesn’t cause significant discomfort. The sample is then sent to a lab for testing.
What Are the Possible Results?
Results are not always definitive on their own. They are often used alongside other tests and symptoms to make a diagnosis. High levels may suggest an autoimmune condition, but they can also be found in people without symptoms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Rheumatoid factor is a marker for autoimmune diseases, particularly rheumatoid arthritis, but it can also appear in other conditions like lupus, Sjogren’s syndrome, or certain infections. While it doesn’t always indicate disease activity, it can help guide treatment decisions and monitor progression over time.
Short name
Rheumatoid Factor (RF)
Frequently asked questions
What Does a Positive Test Mean?
Can Rheumatoid Factor Be Normal in Autoimmune Diseases?
Does Rheumatoid Factor Change Over Time?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy