Rheumatoid factor assay
What is a rheumatoid factor assay?
The rheumatoid factor (RF) assay detects IgM and IgA RFs to IgG in the blood. RFs are a serologic biomarker for the autoimmune disease rheumatoid arthritis, which is a progressive, autoimmune disease that causes pain, swelling, and stiffness in the joints. RFs are typically found in more than 60% percent of people who have rheumatoid arthritis and help to diagnose rheumatoid arthritis although RFs can be found in people with other autoimmune diseases and occasionally even in healthy people.
What is it used for?
A RF antibody test is used to help diagnose rheumatoid arthritis. A RF assay is often conducted along with an ACPA test. Many studies have shown that ACPAs provide a more accurate diagnosis of rheumatoid arthritis compared with RF testing.
Why is a rheumatoid factor assay needed?
You may need this test if you have symptoms of rheumatoid arthritis. These include:
- Joint pain
- Joint stiffness, especially in the morning
- Joint swelling
- Fatigue
- Low-grade fever
What happens during a rheumatoid factor assay?
A small blood sample is needed, which is to be tested in our in-house assay. If your RF antibody results are positive, it means these antibodies are found in your blood, whereas a negative result means no RFs were found.
If you have symptoms of rheumatoid arthritis, and your results show:
- Positive ACPAs and positive RF, it likely means that you have rheumatoid arthritis.
- Positive ACPAs and negative RF, it may mean you are in the early stages of rheumatoid arthritis or will develop it in the future.
- Negative ACPAs and negative RF, it means you are less likely to have rheumatoid arthritis. Your provider may need to do more tests to help find out what is causing your symptoms.