Rheumatoid Arthritis Factor Test (2024)

FAQs

What is rheumatoid arthritis factor test? ›

Overview. A rheumatoid factor test measures the amount of rheumatoid factor in your blood. Rheumatoid factors are proteins made by your immune system that can attack healthy tissue in the body.

A normal, healthy amount of rheumatoid factor is less than 20 units per milliliter (<20 U/mL). Your provider might also refer to your test as being negative or positive. A negative result means you have a normal amount of RF in your blood.

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.

Does Seronegative Rheumatoid Arthritis Exist? The quick answer is yes, seronegative rheumatoid arthritis does exist. A seronegative test for rheumatoid arthritis means that a person tests negative for rheumatoid factor (RF) and cyclic citrullinated peptides (CCP).

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.

For example, a person with high RF levels accompanying rheumatoid arthritis may experience: pain and stiffness in the joints. swelling and inflammation in the joints. a loss of range of motion.

Magnetic resonance imaging (MRI) and ultrasound may help diagnose rheumatoid arthritis in the early stages of the disease.

What mimics rheumatoid arthritis? ›

Lupus and Scleroderma

Systemic lupus erythematosus (lupus) and scleroderma are two autoimmune diseases that can mimic rheumatoid arthritis. Autoimmune diseases are those in which the body's immune system attacks its own cells and tissues.

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)

Patients with rheumatic diseases like Sjogren syndrome, mixed connective tissue diseases, mixed cryoglobulinemia, and systemic lupus erythematosus (SLE) have elevated RFs.

The normal range of RF is often considered to be 0 to 20 IU/ml (also referred to as RF negative) but sometimes a rheumatoid factor greater than or equal to 15 IU/ml is considered to be elevated, or RF positive. A reading above 20 IU/ml is considered high.

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.

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.

An ANA test is commonly used to screen for autoimmune conditions⁴ and the test is often used in both adults and children where a diagnosis of SLE is considered. The rheumatoid factor (RF) test is the most commonly used serological test to determine the presence of RF antibodies.

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.