"Arthritis" is a general term used to describe more than one hundred different conditions, one of them being rheumatoid arthritis (RA). This condition can be mild or very disabling. Like many chronic conditions, the earlier it is diagnosed, the easier it is for treatment to minimize its effects. RA is diagnosed though several different tests including blood tests, specifically a reading of the rheumatoid factor in your blood sample.
Your body contains antibodies, consisting of a type of protein found in your blood and other body fluids. They are part of your immune system and their primary function is to recognize and deal with substances in the body that are foreign. Every antibody is unique and specializes in defending the body against one specific antigen. When your system is functioning properly, it helps to keep you healthy; but in some cases, the body mistakes the self as foreign and attacks itself causing an autoimmune disease. RA is one type of autoimmune disease.
Rheumatoid factor is an antibody that is not normally found in the blood, so your body's production of it may indicate RA or another connective tissue disease. However, it can also be present in healthy individuals with no known disease. By contrast, according to the National Institutes of Health, individuals with these types of diseases can have a low rheumatoid factor or none at all. This is why a combination of tests needs to be done to confirm or rule out a diagnosis.
Conditions With Elevated Rheumatoid Factor
Rheumatoid factor can be detected in those with lupus, Sjogren syndrome, infectious hepatitis, syphilis, infectious mononucleosis, parasites, tuberculosis, liver disease, an infection of the heart, leukemia and sarcoidosis among others. .
Your lab tests will show your rheumatoid factor level in terms of titers or units. Titers measure how diluted your sample of blood must be in order to no longer detect the rheumatoid factor. For example if your titer is 1:20, this means that the factor is able to be detected when one part of your blood sample is diluted by up to twenty parts of a salt solution.
Units measure the amount of light that is blocked by your blood sample in the tube. If your level of RF is high, then the blood sample is cloudy and less light can pass through. What are considered high and low levels can vary depending on the laboratory that completes your tests.
In general a normal titer is a value at or below 1:20; a normal unit level is less than 23 units/mL. Readings above these mean that your RF is elevated. According to the Arthritis Foundation, the higher your RF, the more active and severe your disease is.