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Rheumatoid Factor (Serum/Plasma)

Published: August 9, 2026Updated: August 16, 2026

This test measures the presence of rheumatoid factor, an antibody found in the blood that may indicate rheumatoid arthritis or other autoimmune conditions.

Quick summary

["Rheumatoid factor can help doctors diagnose or monitor certain autoimmune diseases."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
11572-5
Short code
Rheumatoid fact SerPl-aCnc
Synonyms
Rheumatoid fact SerPl-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 your immune system produces in response to certain conditions. Normally, antibodies help fight infections, but in rheumatoid arthritis, they mistakenly attack healthy joint tissues, leading to inflammation and damage. This test detects the presence of these antibodies in your blood.

Why Might You Need This Test?

Doctors may order rheumatoid factor testing if you have symptoms like joint pain, swelling, or stiffness—especially if these occur in the same joints on both sides of your body. It can also be used to monitor disease activity or check for autoimmune conditions like lupus or Sjogren’s syndrome.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. The sample is sent to a lab where it is analyzed using an immunoassay method to detect rheumatoid factor antibodies.

What Do Results Mean?

Results are not always definitive on their own. A positive test suggests a higher likelihood of rheumatoid arthritis or another autoimmune condition, but doctors will consider your symptoms, medical history, and other test results for a full diagnosis.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Rheumatoid factor can be found in some healthy people, especially older adults, and its presence alone doesn’t confirm a diagnosis. However, it’s a useful marker for monitoring disease progression or response to treatment in confirmed autoimmune conditions.

Short name

RF

Frequently asked questions

Can rheumatoid factor test results change over time?
Yes, rheumatoid factor levels can fluctuate. They may rise during active disease phases and sometimes decrease with effective treatment. Regular follow-up testing helps track these changes.
Does diet or lifestyle affect rheumatoid factor test results?
There’s no direct evidence that diet or lifestyle significantly alters rheumatoid factor levels. However, managing symptoms through exercise, stress reduction, and a balanced diet may help overall health, but it won’t change test results directly.
Is a positive rheumatoid factor always linked to rheumatoid arthritis?
No. While rheumatoid factor is strongly associated with rheumatoid arthritis, it can also appear in other autoimmune diseases (like lupus or Sjogren’s) or in some healthy older adults. A doctor will evaluate the full clinical picture.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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