Skip to main navigation Skip to main content Skip to footer For Medicare For Providers For Brokers For Employers Español For Individuals & Families: For Individuals & Families Medical Dental Other Supplemental Explore coverage through work How to Buy Health Insurance Types of Dental Insurance Open Enrollment vs. Special Enrollment See all topics Shop for Medicare plans Member Guide Find a Doctor Log in to myCigna
Home Knowledge Center Wellness Library Rheumatoid Factor (RF) Test

Rheumatoid Factor (RF) Test

Test Overview

A rheumatoid factor (RF) blood test measures the amount of the RF antibody present in the blood. Normally, antibodies are produced by the immune system to help destroy and get rid of invading bacteria and viruses that can cause disease. But the RF antibody can attach to normal body tissue and cause damage.

A high level of RF can be caused by several autoimmune diseases (including rheumatoid arthritis) and some infections. Sometimes a healthy person can have a high RF level.

The amount of RF in blood can be measured in two ways:

Agglutination tests.

One test method mixes blood with tiny rubber (latex) beads that are covered with human antibodies. If RF is present, the latex beads clump together (agglutinate). This method is best used as a first-time screening test for rheumatoid arthritis. Another agglutination test mixes the blood being tested with a sheep's red blood cells that have been covered with rabbit antibodies. If RF is present, the red blood cells clump together. This method is often used to confirm that RF is present.

Nephelometry test.

This test mixes the blood being tested with antibodies that cause the blood to clump if RF is present. A laser light is shined on the tube containing the mixture. Then the amount of light blocked by the blood sample is measured. As levels of RF increase, more clumping occurs. This causes a cloudier sample and allows less light to pass through the tube.

Why It Is Done

Why It Is Done

A test for rheumatoid factor is done to help support a diagnosis of rheumatoid arthritis.

This test is also done to find out whether a child who has polyarticular juvenile idiopathic arthritis has elevated rheumatoid factor. This can help determine the likely progression of the disease, and the best treatment for it.

How To Prepare

How To Prepare

In general, there's nothing you have to do before this test, unless your doctor tells you to.

How It Is Done

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

How long the test takes

The test will take a few minutes.

How It Feels

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Results

You can usually get the results within 24 hours.

A doctor always uses the results of an RF test along with information gained from a medical history and a physical exam before diagnosing rheumatoid arthritis.

The results of the rheumatoid factor (RF) test may be reported in titers or units:

  • A titer is a measure of how much the blood sample can be diluted before RF can no longer be detected. A titer of 1 to 20 (1:20) means that RF can be detected when 1 part of the blood sample is diluted by up to 20 parts of a salt solution (saline). A larger second number means there is more RF in the blood. So a titer of 1 to 80 shows more RF in the blood than a titer of 1 to 20.
  • Nephelometry units show how much light is blocked by the blood sample in the tube. A high level of RF causes the sample to be cloudy, so less light passes through the tube than when the RF level is low. So an RF level of 100 units is higher than one of 40 units.

Normal

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

High values

High RF levels may be caused by:

  • Rheumatoid arthritis.
  • Other autoimmune diseases, such as systemic lupus erythematosus (SLE), scleroderma, Sjögren's syndrome, and vasculitis.
  • Infectious diseases, such as tuberculosis, mononucleosis, syphilis, and malaria.
  • Liver diseases, such as cirrhosis and hepatitis.
  • Infection of the heart (endocarditis).
  • Leukemia.

A small number of people have a high RF level but don't have rheumatoid arthritis. A small number of these people will later have rheumatoid arthritis.

Older adults who don't have rheumatoid arthritis sometimes have a slightly high RF level.

This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.

© 1995-2022 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.

Related Links

Medical Tests: Questions to Ask the Doctor

<cipublic-spinner variant="large"><span>Loading…</span></cipublic-spinner>

Page Footer

I want to...

Get an ID card File a claim View my claims and EOBs Check coverage under my plan See prescription drug list Find an in-network doctor, dentist, or facility Find a form Find 1095-B tax form information View the Cigna Glossary Contact Cigna

Audiences

Individuals and Families Medicare Employers Brokers Providers

Secure Member Sites

myCigna member portal Health Care Provider portal Cigna for Employers Client Resource Portal Cigna for Brokers

Cigna Company Information

About Cigna Company Profile Careers Newsroom Investors Suppliers Third Party Administrators International Evernorth

 Cigna. All rights reserved.

Privacy Legal Product Disclosures Cigna Company Names Customer Rights Accessibility Non-Discrimination Notice [PDF] Language Assistance [PDF] Report Fraud Sitemap

Disclaimer

Individual and family medical and dental insurance plans are insured by Cigna Health and Life Insurance Company (CHLIC), Cigna HealthCare of Arizona, Inc., Cigna HealthCare of Illinois, Inc., and Cigna HealthCare of North Carolina, Inc. Group health insurance and health benefit plans are insured or administered by CHLIC, Connecticut General Life Insurance Company (CGLIC), or their affiliates (see a listing of the legal entities  that insure or administer group HMO, dental HMO, and other products or services in your state). Accidental Injury, Critical Illness, and Hospital Care plans or insurance policies are distributed exclusively by or through operating subsidiaries of Cigna Corporation, are administered by Cigna Health and Life Insurance Company, and are insured by either (i) Cigna Health and Life Insurance Company (Bloomfield, CT); (ii) Life Insurance Company of North America (“LINA”) (Philadelphia, PA); or (iii) New York Life Group Insurance Company of NY (“NYLGICNY”) (New York, NY), formerly known as Cigna Life Insurance Company of New York. The Cigna name, logo, and other Cigna marks are owned by Cigna Intellectual Property, Inc. LINA and NYLGICNY are not affiliates of Cigna.

All insurance policies and group benefit plans contain exclusions and limitations. For availability, costs and complete details of coverage, contact a licensed agent or Cigna sales representative. This website is not intended for residents of New Mexico.

Selecting these links will take you away from Cigna.com to another website, which may be a non-Cigna website. Cigna may not control the content or links of non-Cigna websites. Details