Rheumatoid Factor (IgM) by Immunoassay
This test measures the presence of rheumatoid factor, an antibody found in the blood that may indicate rheumatoid arthritis or other autoimmune conditions.
["Rheumatoid factor can help doctors diagnose certain autoimmune diseases."]
Key facts at a glance
- LOINC
- 13930-3
- Short code
- Rheumatoid fact Titr Snv Aggl
- Synonyms
- Rheumatoid fact Titr Snv Aggl
- Category
- chemistry
- Sample
- fluid
- Container
- Sterile tube
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- aggl
- Specimen volume
- 2-5 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h
- Hemolysis max
- 300
- 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 not always a direct sign of rheumatoid arthritis, it’s often tested when symptoms like joint pain, swelling, or stiffness are present. This test helps doctors assess whether your symptoms may be linked to an autoimmune condition.
Why Might You Need This Test?
Your doctor may order this test if you have symptoms like persistent joint pain, swelling, or fatigue, especially if you also have a history of autoimmune diseases. It can also be part of a routine checkup for people at higher risk, such as those with a family history of rheumatoid arthritis.
How Is the Test Done?
A small blood sample is taken from a vein in your arm. The blood is then processed to detect the presence of rheumatoid factor antibodies using an immunoassay method, which measures their concentration in your serum.
What Are Possible Results?
Results are not always straightforward. A positive test (meaning rheumatoid factor is detected) doesn’t always mean you have rheumatoid arthritis, but it can signal a higher likelihood of an autoimmune condition. Your doctor will consider your symptoms, medical history, and other test results to make a diagnosis.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Rheumatoid factor is commonly associated with rheumatoid arthritis but can also appear in other autoimmune diseases, infections, or even in healthy individuals. While it’s a useful marker, it’s often used alongside other tests to confirm a diagnosis. High levels may prompt further evaluation, including X-rays, physical exams, or additional blood tests to rule out other conditions.
Short name
IgM RF
Frequently asked questions
What Does a Positive Test Mean?
Can Rheumatoid Factor Be False Positive?
How Often Should I Get This Test?
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