Rheumatoid factor (RF)

An elevated rheumatoid factor test result shows that you have a high level of rheumatoid factor in your blood. A higher level of rheumatoid factor in your blood is closely linked with autoimmune diseases, especially rheumatoid arthritis.

But a number of other diseases and conditions can raise rheumatoid factor levels, including:

→ Cancer

→ Chronic infections, such as viral hepatitis B and C

→ Inflammatory lung diseases, such as sarcoidosis

→ Mixed connective tissue disease

→ Sjogren syndrome

→ Systemic lupus erythematosus

Other factors that can cause increased RF:

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. 

Symptoms of rheumatoid arthritis may include:

→ Joint pain

→ Tenderness, swelling, and warmth of the joint

→ Joint stiffness that lasts longer than 30 minutes

→ Fatigue

→ Occasional low fevers

→ Loss of appetite

Not enough to diagnose:

An RF test alone cannot diagnose any conditions. To make a diagnosis, your provider will look at the results of other tests along with your symptoms and medical history.

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.

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.

Interpreting test results:

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.

Keep in mind that this test is never used by itself to definitively diagnose someone with rheumatoid arthritis, Sjögren's syndrome, or any other autoimmune disease. Your RF test results, whether positive or negative, are just one piece of the diagnostic puzzle.

If your tests for anti-CCP and RF both come back negative but you have ongoing symptoms of RA with no other cause or explanation, you may be in the early stages and could receive a diagnosis anyway.

Here's a look at more specific test results regarding rheumatoid arthritis:

Positive RF and/or Anti-CCP:

If you have symptoms of RA, and your RF and/or anti-CCP results are high, the likely result is a diagnosis of seropositive rheumatoid arthritis.

Other diagnostic criteria for seropositive RA include:

→ Elevated CRP or sed rate

→ Inflammatory arthritis in three or more joints

→ Symptoms that have persisted for more than six weeks

→ All other diseases with similar symptoms have been ruled out

In general, the higher your RF level, the more severe your disease is likely to be, but this is not a rule.

Negative RF and Anti-CCP:

If you had negative RF and anti-CCP tests but you have symptoms consistent with rheumatoid arthritis and other possible diseases have been ruled out, the likely result is a diagnosis of seronegative rheumatoid arthritis, which is less common than seropositive RA.

This means that you don't have the RF and anti-CCP antibodies in your blood, but you meet the other diagnostic criteria.

Negative RF:

If you have signs and symptoms of RA and you had a negative RF test but no other tests at the same time, the next likely step is an anti-CCP test. If it's positive, the likely diagnosis is seropositive RA, provided you meet the rest of the diagnostic criteria.

Juvenile RA:

As with adult RA, healthcare providers look at the total picture, including physical symptoms and a variety of test results. JRA has seven distinct subtypes, each with its own diagnostic criteria. RF is positive in some and negative in others.

Sjögren's Syndrome:

If you have negative anti-Ro/SS-A and anti-La/SS-B antibody tests but a positive RF test and a positive ANA result, the likely result is a diagnosis of Sjögren's syndrome.

Follow up:

If your RF test and/or anti-CCP test came back positive but you don't have RA symptoms, you're not necessarily in the clear. It's possible that you may develop RA over time. This is more likely if your levels are high and substantially more likely when both tests are positive, in which case, your healthcare provider may run these tests again at a later time.

In cases where your healthcare provider is looking for Sjögren's syndrome, if your RF test and anti-Ro/SSA and anti-La/SSB antibody tests are all negative and you don't already have an established autoimmune disease, your healthcare provider will need to consider another cause of your symptoms.

Other autoimmune diseases that can raise rheumatoid-factor levels include:

→ Systemic lupus erythematosus

→ Scleroderma

→ Polymyositis

→ Dermatomyositis

→ Mixed connective tissue disease

→ Mixed cryoglobulinemia syndrome (types II and III)

A number of infections or other medical conditions can be associated with positive rheumatoid factor test results, too. However, the RF test is not used to diagnose any of these other autoimmune diseases, infections, or medical conditions.

Some of them include:

→ Bacterial endocarditis

→ Tuberculosis

→ Syphilis

→ Hepatitis

→ HIV/AIDS

→ Mononucleosis

→ Liver cirrhosis and other liver diseases

→ Sarcoidosis

→ Certain kidney diseases

→ Cancers such as multiple myeloma and leukemia

→ Lung diseases

→ Parasitic infections