Rheumatoid Arthritis Factor

Test Quick Guide

The test detects rheumatoid factor (RF) in your blood. This protein is part of a normal immunogenic response to the presence of a foreign entity, such as bacteria or a virus, forming a complex that the immune system can remove.

If you have rheumatoid arthritis (RA) you will develop an abnormal protein called an autoantibody, which can result in RA at high levels. While normal antibodies attack pathogens like bacteria and viruses, autoantibodies such as RF mistakenly attack the body’s healthy cells and tissues.

Testing for RF is most often used in conjunction with other laboratory and imaging tests to diagnose RA or Sjögren’s syndrome. Some patients with RA may have low levels of RF, while 4% of some healthy people can have a positive RF.

About the Test

Purpose of the test

Testing for RF determines if you have it in your blood. Some healthy people have detectable RF. But a positive result can also indicate an underlying health condition and may warrant additional diagnostic testing if you have other signs or symptoms of an autoimmune disorder. An RF test can help doctors diagnose autoimmune disorders and estimate disease severity:

  • Diagnosing autoimmune disorders: This testing may be appropriate if you have symptoms of RA, Sjögren’s syndrome, or another autoimmune disorder. Your doctor may recommend a test for RF if you are experiencing pain and inflammation in multiple joints that aren’t due to another condition.
  • Estimating disease severity: RF testing can also provide doctors with information about the severity of RA. If you have higher levels of RF, you are more likely to have severe RA, a more aggressive disease causing erosion of joints, development of rheumatoid nodules, and damaging inflammation of the blood vessels. RF can also affect parts of the body outside of the joints, such as the lungs, eyes, and heart.

Although treatment for RA may lower the amount of RF in the blood, repeated testing for RF is not typically used to monitor you if receiving treatment for RA.

What does the test measure?

RF testing measures the amount of RF in the blood. There are several ways to measure RF, one of which is an antibody titer test. These tests detect how much of a specific type of antibody is present in the blood, with results expressed as a ratio. Generally, a normal titer is about 1:80, whereas a higher (>1:80) is a positive result. Results can vary from lab to lab.

The development of RF and how it affects the body is not well understood. Researchers believe that RFs may result from the body’s response to pathogens, like bacteria or viruses, and other triggers that confuse the immune system.

When should I get a rheumatoid factor test?

A doctor may recommend an RF test if you are experiencing symptoms of RA, which include:

  • Joint symptoms, including pain and swelling
  • Morning stiffness for 30 minutes or longer
  • Tiredness or fatigue
  • Intermittent fever
  • Appetite loss
  • Weight loss
  • Weakness
  • Dry eyes and mouth
  • Firm lumps beneath the skin

Some factors that may increase the risk of RA include age (adults in 60s), gender (females are two to three times more likely to have RA), smoking, women who have not given birth, children of mothers who smoked, and obesity. A decreased risk has been associated with women who breastfeed their babies.

RF testing is not a screening test for RA if you don’t have symptoms. Usually, if you test positive for RF but don’t have symptoms, you will never go on to develop RA.

Doctors may also order an RF test while testing for other health conditions. Other conditions in which RF testing may be used include:

  • Sjögren’s syndrome
  • Lupus
  • Juvenile arthritis
  • Scleroderma
  • Certain infections, including mononucleosis or tuberculosis
  • Certain types of cancer, including leukemia
  • Hepatitis C
  • Endocarditis
  • Sarcoidosis

Finding a Rheumatoid Factor Test

How can I get a rheumatoid factor test?

A doctor orders RF testing. Your doctor may suggest the test alone, but usually, it is used along with other tests to evaluate you for an autoimmune disorder. RF testing requires a blood sample normally drawn in a doctor’s office, hospital, or laboratory.

Can I take the test at home?

While not common, at-home testing for RF can detect the level in the blood. Taking an at-home RF test involves pricking a finger and collecting a small blood sample. The blood sample is then sent to a laboratory for analysis, and the results are returned to you via the company’s website or smartphone application.

At-home testing kits may combine an RF test with a test for cyclic citrullinated peptide (CCP) antibodies. While both RF and CCP antibodies are biomarkers that may indicate your likelihood of having RA, neither can definitively diagnose the condition without clinical evaluation. Doctors use the results of these tests in combination with other factors to diagnose RA or other autoimmune disorders.

How much does the test cost?

The cost of RF testing depends on whether or not your health insurance covers this type of testing. Costs can also vary based on where the test is conducted and whether RF testing is combined with other tests. A rheumatoid arthritis factor test costs $49 from Testing.com.

If you have health insurance, fees for the blood draw, laboratory analysis, and office visits may be included in the cost of RF testing. Your health insurance often covers most or all of these costs when a doctor prescribes the test. It’s important to talk to your health insurance company to understand deductibles or copays that may be required.

At-home tests may not be covered by health insurance and cost around $100.

Taking a Rheumatoid Factor Test

An RF test is performed on a blood sample typically taken from a vein in your arm. The blood sample can be drawn in a doctor’s office, health clinic, or laboratory.

A blood sample is obtained for an at-home RF test by pricking a finger and collecting the sample as instructed in a test kit.

Before the test

Generally, taking an RF test requires no special preparations. You may still find it helpful to talk to your doctor before the test about any medications or supplements you are taking, as well as any questions or concerns about the RF test.

Before taking an at-home RF test, read the instructions in the test kit carefully and consult the testing company or your doctor if you need additional guidance.

During the test

To obtain the necessary blood sample for an RF test, a sample of blood is drawn from a vein in your arm, usually inside the elbow or on the back of the hand.

The health care provider conducting the blood draw will first locate an appropriate vein. Next, the provider will place an elastic band a few inches above the vein to increase blood flow. The skin is then cleaned and a needle is inserted into the vein. Blood is collected in a test tube or vial before the elastic band is removed and the needle is withdrawn.

This process typically takes less than five minutes. You may feel stinging when the needle is inserted and removed and some throbbing at the site after the blood is drawn.

All necessary materials for sample collection are provided in the test kit for an at-home RF test. Begin testing by cleaning your fingertip and pricking it with a provided lancet or needle to obtain a drop of blood. Then, you will put a few drops of blood into a collection device or test tube. The collection device is then packaged and sent to a lab by mail.

After the test

After completing a blood draw, a health care provider will apply a bandage and pressure to stop any bleeding at the site of the blood draw. There is little risk in having a blood draw. You may experience temporary pain or minor bruising. There are no restrictions on activities after RF testing.

For an at-home RF test, you can apply a bandage to your fingertip to stop bleeding after collecting the blood sample.

Rheumatoid Factor Test Results

Receiving test results

Results are normally available within a few business days of taking an RF test. They may be shared with you via phone, mail, or electronically. In some cases, doctors may wait to share the results of RF testing until other testing is completed.

Results from at-home RF testing may take additional time as the test sample must first be mailed to the appropriate laboratory. Test reports may be available through the company’s website or a smartphone app. Some at-home testing companies connect you to a health professional for support in understanding the test result.

Interpreting test results

After an RF test is completed, test results are reported as either positive or negative. A numerical or titer value may be provided to indicate the level of RF detected in the blood. Negative results may also be called normal, while positive results may be called abnormal.

Reference ranges for this test vary by laboratory and the type of RF test performed in the analysis. It’s important to use the reference ranges provided by an individual laboratory.

Because RF testing is rarely used alone, the results of an RF test should be interpreted with caution. A negative test result indicates that little to no RF was found in the blood, but this does not always rule out an underlying health issue. Up to 20% of people with RA may have a negative RF test result, and their results may change over time.

Testing positive for RF may indicate an underlying health condition but is insufficient to diagnose it on its own. Around 4% of healthy people have RF detected in their blood. Positive results may also be related to an underlying autoimmune disorder, certain infections, and some types of cancer.

While high levels alone cannot diagnose any condition, research suggests that the higher the amount of RF in the blood, the greater the likelihood you have an autoimmune disorder.

To diagnose the cause of your symptoms, doctors often combine RF testing with a physical exam, imaging tests, and laboratory tests such as CCP antibody testing, antinuclear antibody (ANA) testing, and a synovial fluid analysis. Up to 30% of RA patients may be negative for RF but often positive for antiCCP, an abnormality that may precede overt symptoms of RA.

Diagnosing autoimmune disorders can be complex. It’s important to work with a doctor or consult with a rheumatologist, a doctor specializing in diagnosing and treating autoimmune disorders and other conditions of the joints, muscles, and bones. A rheumatologist can help you understand your results, as well as answer questions about the process of diagnosing autoimmune disorders.

Some questions that may be helpful to review with a doctor include:

  • How does my test result help me understand the cause of my symptoms?
  • Based on my test result, what is the likelihood that I have RA or another autoimmune disorder?
  • Do I need any follow-up tests based on my test result?

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