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Rheumatoid Factor (IgM) by Latex Agglutination

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

This test measures the presence of rheumatoid factor, an antibody found in some people with rheumatoid arthritis or other autoimmune conditions.

Quick summary

["Rheumatoid factor may help identify potential autoimmune diseases."]

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

Key facts at a glance

LOINC
25745-1
Short code
Rheumatoid fact Fld Ql Shp Aggl
Synonyms
Rheumatoid fact Fld Ql Shp Aggl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
sheep-cell-aggl
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 (RF) is an antibody that can attack healthy cells in your body. While it’s not always a definitive sign of rheumatoid arthritis, it can be present in people with autoimmune diseases like lupus or Sjogren’s syndrome. This test checks for IgM rheumatoid factor, which is one of the most common types.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms like joint pain, swelling, or fatigue, or if they suspect an autoimmune condition. It’s also sometimes used as part of a broader evaluation for unexplained inflammation or connective tissue disorders.

How Is the Test Performed?

A small blood sample is drawn from a vein, usually in your arm. The blood is then tested in a lab using a method called latex agglutination, which detects the presence of rheumatoid factor antibodies.

What Do the Results Mean?

A positive result (meaning the test detected rheumatoid factor) doesn’t always mean you have rheumatoid arthritis, but it can signal an increased risk of autoimmune diseases. False positives can occur, so results are often reviewed in the context of your symptoms and other tests.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Rheumatoid Factor’s Role in Health

Short name

Rheumatoid Factor (IgM)

Frequently asked questions

How often will I need this test?
Rheumatoid factor levels can change over time, especially if you’re undergoing treatment for an autoimmune condition. Your doctor may recommend retesting if symptoms worsen or improve, or if they suspect a different diagnosis.
What are the possible side effects of the blood draw?
Most people experience only mild discomfort or bruising at the injection site. Rarely, there may be slight swelling or pain, but these usually resolve quickly. If you have a bleeding disorder or take blood thinners, let your doctor know before the test.
Can I eat or drink before this test?
You can eat and drink normally before this test unless your doctor instructs otherwise. No special preparation is needed, but always follow your healthcare provider’s specific instructions.
  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