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Rheumatoid Factor (IgM) by Immunoassay (Serum/Plasma)

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

This test measures the presence of rheumatoid factor (IgM), an antibody linked to rheumatoid arthritis and other autoimmune conditions.

Quick summary

["IgM rheumatoid factor may help diagnose or monitor autoimmune diseases."]

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

Key facts at a glance

LOINC
111069-1
Short code
Rheumatoid fact Msmt Snv
Synonyms
Rheumatoid fact Msmt Snv
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 (RF) is an antibody produced by the immune system in some people with autoimmune diseases, including rheumatoid arthritis. IgM rheumatoid factor is one type of this antibody. While not all people with rheumatoid arthritis have elevated levels, it can be a useful marker for screening or monitoring certain conditions.

Why Might You Need This Test?

Your healthcare provider may order this test if you have symptoms of rheumatoid arthritis (e.g., joint pain, swelling, stiffness) or other autoimmune conditions. It can also be used as part of a broader evaluation for unexplained joint or systemic symptoms.

How Is the Test Performed?

A blood sample is drawn from a vein in your arm. The serum or plasma is then tested using an immunoassay method to detect rheumatoid factor antibodies.

What Do Results Mean?

Results are qualitative (positive or negative) rather than numeric. A positive result suggests the presence of rheumatoid factor, which may indicate an increased risk for autoimmune diseases. However, it is not definitive on its own and should be interpreted alongside clinical findings and other tests.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgM Rheumatoid Factor

Frequently asked questions

What Are Common Causes of Positive Results?
Positive rheumatoid factor results are most commonly associated with rheumatoid arthritis, but they can also occur in other autoimmune diseases (e.g., lupus, Sjogren’s syndrome) or in some infections (e.g., hepatitis, syphilis). False positives may occur in older adults or with certain medications.
What Are Common Causes of Negative Results?
A negative result means no detectable rheumatoid factor was found in this sample. However, rheumatoid factor may be absent in people without autoimmune diseases or those in early stages of disease. It does not rule out rheumatoid arthritis or other conditions definitively.
How Often Should I Get This Test Retested?
Follow your healthcare provider’s recommendations. If you have symptoms or risk factors, retesting may be needed to monitor disease progression or response to treatment. Results should always be discussed with your provider.
  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