Rheumatoid Factor (Serum) – Immunoassay
This test measures the presence of antibodies called rheumatoid factor in your blood, which may indicate inflammation linked to rheumatoid arthritis or other autoimmune conditions.
["Rheumatoid factor helps doctors assess possible autoimmune diseases."]
Key facts at a glance
- LOINC
- 5297-7
- Short code
- Rheumatoid fact Ser Ql LA
- Synonyms
- Rheumatoid fact Ser Ql 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 Does This Test Measure?
Rheumatoid factor is an antibody that targets part of your own immune system proteins. While it can be found in some healthy people, higher levels often suggest an autoimmune condition like rheumatoid arthritis, where the body mistakenly attacks its own joints and tissues.
Why Might This Test Be Ordered?
Your healthcare provider may order this test if you have symptoms like joint pain, swelling, stiffness, or fatigue, or if you have a family history of autoimmune diseases. It can also be used as part of a broader evaluation for conditions like lupus or other inflammatory disorders.
How Is the Test Performed?
A blood sample is drawn from a vein, usually in your arm. The blood is then sent to a lab for testing using an immunoassay method to detect rheumatoid factor antibodies.
What Are Common Results and Next Steps?
Results are not always definitive on their own. A positive result (detecting rheumatoid factor) increases suspicion for autoimmune conditions, but further testing (like X-rays, physical exams, or other blood tests) is often needed to confirm a diagnosis.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Rheumatoid factor is not specific to rheumatoid arthritis—it can appear in other autoimmune diseases or even in some infections. High levels may prompt additional testing (e.g., anti-CCP antibodies, erythrocyte sedimentation rate) to narrow down the cause. Always discuss results with your doctor, as they’ll consider your symptoms, medical history, and other test results.
Short name
Rheumatoid Factor (RF)
Frequently asked questions
What does a positive rheumatoid factor mean?
Yes, rheumatoid factor can be negative in some people with rheumatoid arthritis. It’s not a definitive test for the condition, so doctors rely on a combination of tests and clinical findings to make a diagnosis.
Ask your doctor if you have any symptoms of joint pain, swelling, or fatigue, or if you notice unexplained weight changes, fatigue, or other concerning signs. They may recommend further testing (like anti-CCP antibodies, X-rays, or other bloodwork) based on your results and medical history.
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