What is the RA factor?

An RA factor is the amount of rheumatoid factor, or proteins found in the blood that may attack healthy tissues in the human body. High levels of RA factor often signal an autoimmune disorder, but some people who have a high RA level are healthy, according to the Mayo Clinic.

Additionally, some people with rheumatoid arthritis have low levels of rheumatoid factor. Scientists are not sure why this occurs, reports the Mayo Clinic. Most commonly, a high amount of RA in the blood is associated with rheumatoid arthritis, but there are many other medical issues that may cause high rheumatoid factor, such as cancer, chronic infections, cirrhosis and inflammatory lung diseases, according to the Mayo Clinic.