Rheumatoid factor (RF) is a blood test that measures the amount of the RF antibody in the blood.
How the Test is Performed
Most of the time, blood is drawn from a vein located on the inside of the elbow or the back of the hand.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin.
- The blood collects in a small glass tube called a pipette, or onto a slide or test strip.
- A bandage is put over the spot to stop any bleeding.
How to Prepare for the Test
You do not need to take special steps before this test.
How the Test will Feel
You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.
Why the Test is Performed
This test is most often used to help diagnose rheumatoid arthritis or Sjögren syndrome.
Results are usually reported in one of two ways:
- Value, normal less than 15 IU/mL
- Titer, normal less than 1:80 (1 to 80)
If the result is above the normal level, it is positive. A low number (negative result) most often means you do not have rheumatoid arthritis or Sjögren syndrome. However, some people who do have these conditions still have a negative or low RF.
Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.
What Abnormal Results Mean
An abnormal result means the test is positive, which means a higher level of RF has been detected in your blood.
- Many people with rheumatoid arthritis or Sjögren syndrome have positive RF tests.
- The higher the level, the more likely one of these conditions is present. There are also other tests that can be done to help make the diagnosis.
- Not everyone with a higher level of RF has rheumatoid arthritis or Sjögren syndrome.
Your provider should also do another blood test (anti-CCP antibody), to help diagnose rheumatoid arthritis (RA). Anti-CCP antibody is more specific for RA than RF. A positive test for CCP antibody means RA is probably the correct diagnosis.
People with the following diseases may also have higher levels of RF:
- Hepatitis C
- Systemic lupus erythematosus
- Dermatomyositis and polymyositis
- Mixed cryoglobulinemia
- Mixed connective tissue disease
Higher-than-normal levels of RF may be seen in people with other medical problems. However, these higher RF levels cannot be used to diagnose these other conditions:
- AIDS, hepatitis, influenza, infectious mononucleosis, and other viral infections
- Certain kidney diseases
- Endocarditis, tuberculosis, and other bacterial infections
- Parasite infections
- Leukemia, multiple myeloma, and other cancers
- Chronic lung disease
- Chronic liver disease
In some cases, people who are healthy and have no other medical problem will have a higher-than-normal RF level.
Aletaha D, Neogi T, Silman AJ, et al. 2010 Rheumatoid arthritis classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative. Ann Rheum Dis. 2010;69(9):1580-1588. PMID: 20699241
Darrah E, Rosen A, Andrade F. Autoantibodies in rheumatoid arthritis. In: Firestein GS, Budd RC, Gabriel SE, Koretzky GA, McInnes IB, O'Dell JR, eds. Firestein & Kelley's Textbook of Rheumatology. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 59.
Hoffmann MH, Trouw LA, Steiner G. Autoantibodies in rheumatoid arthritis. In: Hochberg MC, Gravallese EM, Silman AJ, Smolen JS, Weinblatt ME, Weisman MH, eds. Rheumatology. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 99.
Mason JC. Rheumatic diseases and the cardiovascular system. In: Zipes DP, Libby P, Bonow RO, Mann DL, Tomaselli GF, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 11th ed. Philadelphia, PA: Elsevier; 2019:chap 94.
Pisetsky DS. Laboratory testing in the rheumatic diseases. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 242.
Last reviewed on: 5/2/2021
Reviewed by: Diane M. Horowitz, MD, Rheumatology and Internal Medicine, Northwell Health, Great Neck, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
What is an acceptable rheumatoid factor? ›
Results are usually reported in one of two ways: Value, normal less than 15 IU/mL. Titer, normal less than 1:80 (1 to 80)
Negative levels do not exclude the disease, and positive levels do not guarantee the diagnosis. The normal range of RF is from 0-20 IU/ml. RF above 20 IU/ml is not considered enough to diagnose RA, as there other reasons the RF level may be elevated.Can you have a high rheumatoid factor and not have rheumatoid arthritis? ›
Rheumatoid factors are proteins that the immune system produces when it attacks health tissue. About half of all people with rheumatoid arthritis have high levels of rheumatoid factors in their blood when the disease starts, but about 1 in 20 people without rheumatoid arthritis also test positive.Is rheumatoid factor less than 10 normal? ›
Most medical centers consider the normal range of rheumatoid factor to be up to 10 IU/mL or 20 IU/mL, says rheumatologist Steffan Schulz, MD, assistant professor of clinical medicine with Penn Medicine in Philadelphia.Is rheumatoid factor positive in lupus? ›
Rheumatoid factor (RF) is found commonly in patients with systemic lupus erythematosus (SLE), and has been associated with a more benign disease course.How do you read rheumatoid factor results? ›
If the result is above the normal level, it is positive. A low number (negative result) most often means you do not have rheumatoid arthritis or Sjögren syndrome. However, some people who do have these conditions still have a negative or low RF. Normal value ranges may vary slightly among different laboratories.What percentage of patients with RA have a positive RF? ›
Rheumatoid factor (RF) is used in the diagnosis of rheumatoid arthritis (RA). RF results are positive in approximately 75% of patients with RA, although RF is not etiologically related to RA. High RF titers indicate a poorer prognosis, as patients with higher RF levels tend to have more severe disease.What are the 7 diagnostic criteria for RA? ›
The new criteria are as follows: 1) morning stiffness in and around joints lasting at least 1 hour before maximal improvement; 2) soft tissue swelling (arthritis) of 3 or more joint areas observed by a physician; 3) swelling (arthritis) of the proximal interphalangeal, metacarpophalangeal, or wrist joints; 4) symmetric ...What cancers have high rheumatoid factor? ›
Non-Hodgkin's Lymphoma and Hodgkin's Disease.What can be misdiagnosed as rheumatoid arthritis? ›
People with inflammatory bowel disease (IBD) — including ulcerative colitis and Crohn's disease — may develop peripheral arthritis that affects the knuckles and can be mistaken for RA. IBD-related arthritis can also cause symptoms in the elbows, wrists, knees, and ankles.
What autoimmune mimics rheumatoid arthritis? ›
The autoimmune diseases systemic lupus erythematosus and scleroderma often present with joint involvement that mimics rheumatoid arthritis. While lupus and scleroderma are two different diseases, they often overlap with one another.Can you be wrongly diagnosed with rheumatoid arthritis? ›
Misdiagnosis of Rheumatoid Arthritis Is Common. Many rheumatic diseases have overlapping symptoms, and that can complicate the effort to obtain an accurate diagnosis for RA. Some diseases are complex. They may have overlapping characteristics with other conditions, making diagnosis more difficult.Is a rheumatoid factor of 12 normal? ›
The "normal" range (or negative test result) for rheumatoid factor is less than 14 IU/ml. Any result with values 14 IU/ml or above is considered abnormally high, elevated, or positive.Is 15 a good rheumatoid factor? ›
The normal range of rheumatoid factor levels is usually between < 14 and < 20 IU/mL. A level above these values is considered a positive result and may indicate rheumatoid arthritis or other disorders [9, 10, 11].What are the markers for rheumatoid arthritis? ›
The main clinically useful biologic markers in patients with RA include rheumatoid factors (RF), anti-cyclic citrullinated peptide (anti-CCP) antibodies, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).How does a rheumatologist diagnose lupus? ›
If your doctor suspects you have lupus based on your symptoms, a series of blood tests will be done in order to confirm the diagnosis. The most important blood screening test is ANA. If ANA is negative, you don't have lupus. However, if ANA is positive, you might have lupus and will need more specific tests.What's worse lupus or RA? ›
Neither RA nor lupus is "worse" than the other. They are different conditions and require treatment accordingly. Lupus and RA patients can have a mild or severe form of either disease.Is rheumatoid factor positive in fibromyalgia? ›
Positivity of RF and anti-CCP was evaluated between the groups with or without FMS in RA patients. Rheumatoid factor was positive in 67.9% and 75.5% and anti-CCP was positive in 71.7% and 76.5% of the patients with or without FMS, respectively (p>0.05).Can rheumatoid factor change? ›
Your rheumatoid arthritis markers may change over time from negative to positive, since many people with seronegative rheumatoid arthritis begin to develop RF or ACPA antibodies. “It happens, but it's not that common,” says Dr. Domingues.Do all RA patients have RF? ›
Most people with RA -- between 60% and 80% -- make RF and anti-CCPs. But those antibodies are also found with other diseases. So by themselves, they aren't enough to diagnose RA. The levels of RF and anti-CCPs can be different for everyone.
Can you have rheumatoid arthritis with normal RF? ›
Many people with rheumatoid arthritis have little or no rheumatoid factor. If you have symptoms of rheumatoid arthritis, but your RF test results are normal, your provider may order more tests to make a diagnosis. A positive (abnormal) result means that a higher level of rheumatoid factor was found in your blood.What is the most specific test for rheumatoid arthritis? ›
Anti-CCP antibody test (ACCP or CCP). This test is for a type of autoantibody called cyclic citrullinated peptide (CCP) antibodies, which can be found in the blood of 60% to 80% of people with rheumatoid arthritis.What is considered early diagnosis of RA? ›
Early RA – This term is generally applied to disease that is between a few weeks and one year in its progression. Some studies, however, consider "early arthritis" to be disease with six months of duration or less. The turning point to chronic RA begins after 12 weeks.What is the gold standard for rheumatoid arthritis? ›
Methotrexate: a gold standard for treatment of rheumatoid arthritis.Which is the more accurate test for diagnosis of RA? ›
Cyclic citrullinated peptide (CCP)laboratory testing is typically more accurate for rheumatoid arthritis than the older rheumatoid factor (RF) test.Can stress cause high rheumatoid factor? ›
Stress can trigger flare-ups of RA, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) . Flare-ups of RA can also: increase your risk of joint damage. contribute to poorer long-term outcomes.What infections cause high rheumatoid factor? ›
They are also frequently found to be elevated in some non-rheumatic diseases, especially chronic infections like hepatitis C, tuberculosis, and subacute infective endocarditis. Sarcoidosis and malignancies like primary sclerosing cholangitis also have RF elevation.Can rheumatoid factor go away? ›
No, rheumatoid arthritis doesn't go away. It's a condition you'll have for the rest of your life. But you may have periods where you don't notice symptoms. These times of feeling better (remission) may come and go.How do doctors tell the difference between arthritis and rheumatoid arthritis? ›
The main difference between osteoarthritis and rheumatoid arthritis is the cause behind the joint symptoms. Osteoarthritis is caused by mechanical wear and tear on joints. Rheumatoid arthritis is an autoimmune disease in which the body's own immune system attacks the body's joints.Can vitamin D deficiency mimic rheumatoid arthritis? ›
Studies also have found that a lack of vitamin D is linked to rheumatoid arthritis, an autoimmune disease characterized by swollen, aching joints and numbness and tingling in the hands and feet.
Can you test positive for rheumatoid arthritis and not have it? ›
No single blood test can reliably diagnose RA. Some healthy people test positive for anti-CCPs, while others who have RA have negative test results. Blood tests are just one of several factors, including a medical history, physical exam and X-rays, that help doctors diagnose the disease.Can lupus and RA be confused? ›
Both conditions affect your joints, so it's easy to confuse them. In fact, lupus has been called "the great imitator" because it can seem a lot like not just RA but many other diseases, too. So it's important to know how RA and lupus do and do not resemble each other.Does rheumatoid arthritis show up on ANA? ›
Antinuclear antibody test (ANA)
Since RA is an autoimmune disease, many people with RA have positive ANA tests. However, a positive test doesn't mean you have RA. Many people have positive, low-level ANA tests without clinical evidence of RA.
The main link between fibromyalgia and rheumatoid arthritis is that they have similar symptoms and cause pain. Their similarities can make diagnosis difficult, so it is possible for fibromyalgia to be misdiagnosed as rheumatoid arthritis.What else could it be besides rheumatoid arthritis? ›
Nonetheless, RA is not the only condition which includes joint inflammation, fever, and fatigue as its symptoms. In fact, these are also common in several other conditions like Fibromyalgia, Osteoarthritis, Ankylosing Spondylitis, Psoriatic Arthritis, Gout, Lupus, and infectious arthritis.How do I know if I have rheumatoid arthritis or something else? ›
Signs and symptoms of rheumatoid arthritis may include: Tender, warm, swollen joints. Joint stiffness that is usually worse in the mornings and after inactivity. Fatigue, fever and loss of appetite.Is rheumatoid arthritis a big deal? ›
RA is a very serious autoimmune disease, in which your immune system mistakenly attacks your own body's tissues and causes severe joint pain, stiffness, severe fatigue, and sometimes deformity, usually in the hands, shoulders, knees, and/or feet. It affects men, women, and children of all ages.What is a high number for rheumatoid arthritis? ›
A rheumatoid factor level over 100 is strongly associated with autoimmune diseases like RA. To compare, typical findings are less than 60 u/ml. In addition to RA, a high rheumatoid factor can also point to cancer, chronic infections, Sjögren's disease, bacterial endocarditis, or other autoimmune disorders.Is 16 a high rheumatoid factor? ›
The level of 16 is very very low. The blood test is not enough to make the diagnosis, especially not at this low level.What does it mean if my rheumatoid factor is less than 15? ›
Though there is some variation depending on the lab, a normal level of rheumatoid factor is typically considered to be less than 15 or 20 IU/mL. A number above that is considered to be abnormal, and means you are positive for rheumatoid factor.
What does a rheumatoid factor of 20 mean? ›
Reference ranges may vary, but normally values >20 IU/ml are considered positive; however, most RA patients have values >160 IU. As with rheumatoid factor, values >20 are normally considered positive; however, most RA patients will have strongly positive results (i.e., >60 units).Can you have rheumatoid arthritis without inflammation markers? ›
As mentioned above, at the time of presentation many patients with RA have normal inflammatory markers; moreover, about 60% are seronegative for rheumatoid factor and more than 70% have normal plain radiographs. Thus negative results with these do not exclude the diagnosis.Is a rheumatoid factor of 35 high? ›
The normal range of rheumatoid factor levels is usually between < 14 and < 20 IU/mL. A level above these values is considered a positive result and may indicate rheumatoid arthritis or other disorders [9, 10, 11].What levels are high with rheumatoid arthritis? ›
People with rheumatoid arthritis often have an elevated erythrocyte sedimentation rate (ESR, also known as sed rate) or C-reactive protein (CRP) level, which may indicate the presence of an inflammatory process in the body.What is the highest RA factor you can have? ›
Some doctors define normal RF levels as 0–20 units per milliliter (U/ml) of blood. On the other hand, one 2012 study designated the upper limit of regular levels as 25 U/ml . A person's risk of developing rheumatoid arthritis typically increases with their RF level.What cancers cause high RA factor? ›
A number of studies show that people with RA have roughly double the average risk for developing lymphoma, a group of cancers that arise in the blood. This is likely caused by chronic inflammatory stimulation of the immune system.Can your rheumatoid factor go down? ›
Your rheumatoid arthritis markers may change over time from negative to positive, since many people with seronegative rheumatoid arthritis begin to develop RF or ACPA antibodies. “It happens, but it's not that common,” says Dr. Domingues.How quickly does rheumatoid arthritis spread? ›
The symptoms of rheumatoid arthritis often develop gradually over several weeks, but some cases can progress quickly over a number of days. The symptoms vary from person to person. They may come and go, or change over time. You may experience flares when your condition deteriorates and your symptoms become worse.