Rheumatoid factor (RF) (2023)

FAQs

What is an acceptable rheumatoid factor? ›

Normal Results

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.

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.

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.

Rheumatoid factor (RF) is found commonly in patients with systemic lupus erythematosus (SLE), and has been associated with a more benign disease course.

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.

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.

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 ...

Non-Hodgkin's Lymphoma and Hodgkin's Disease.

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.

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.

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.

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].

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).

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.

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.

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).

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.

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.

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.

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.

Methotrexate: a gold standard for treatment of rheumatoid arthritis.

Cyclic citrullinated peptide (CCP)laboratory testing is typically more accurate for rheumatoid arthritis than the older rheumatoid factor (RF) test.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The level of 16 is very very low. The blood test is not enough to make the diagnosis, especially not at this low level.

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).

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.

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].

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.

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.

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.

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.

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.