| There are four main antibodies in the blood. They are | | | | with RA will be positive for RF at some time during the |
| IgG, IgM, IgA, and IgE. An antibody is a protein made by | | | | course of their disease. While RF by itself is not |
| white blood cells. The purpose of an antibody is to fight | | | | diagnostic of RA, it is one of many criteria used to help |
| off infections and to destroy any other invaders that | | | | with making the diagnosis. |
| might do harm. For example, say, you get a splinter. | | | | The level of RF is also a good prognostic indicator |
| Your white blood cells rush to that area and mount an | | | | since high levels of RF are associated with increased |
| acute inflammatory response. Antibodies are produced | | | | disease severity, the development of erosions |
| to attack bacteria. The area around the splinter | | | | (damage to the joint), involvement of other organ |
| becomes swollen, red, and hurts. Your immune system | | | | systems, and disability. |
| is doing its job. | | | | RF is not specific for RA and can be found in patients |
| Sometimes, though, a person can develop an | | | | with other diseases such as systemic lupus |
| autoimmune disease, meaning a disease where | | | | erythematosus, spondyloarthropathy, inflammatory |
| antibodies are created that are abnormal and are | | | | muscle disease, viral infections, vasculitis, reactive |
| directed against the bodies own tissues. This creates a | | | | arthritis, mixed cryoglobulinemia, sarcoidosis, bacterial |
| situation where there is chronic ongoing inflammation. | | | | endocarditis, syphilis, and leprosy. RF can also be |
| The inflammation doesn't shut off. This inflammation | | | | present in older people who have no other illnesses. |
| eventually causes damage to the body. | | | | A more specific test for rheumatoid arthritis that is |
| Rheumatoid arthritis (RA) is an autoimmune disease. | | | | often ordered along with the RF is the anti-cyclic |
| One of the first abnormalities in RA is the creation of | | | | citrullinated peptide antibody (anti-CCP). The anti-CCP |
| rheumatoid factor. The rheumatoid factor (RF) is an | | | | is probably less sensitive than the RF so both tests |
| antibody directed against another antibody called IgG. | | | | probably should be ordered at the same time. The |
| Most often the rheumatoid factor antibody is an IgM | | | | anti-CCP can be negative in patients with RA, so it's |
| antibody. Sometimes it can be an IgA or an IgG. The | | | | important to look at the big picture rather than focus |
| level of rheumatoid factor can be measured using a | | | | on the results of one test. |
| specific blood test. | | | | Finally, since RF may be IgG, IgM, or IgA, it's important |
| The RF is not diagnostic for rheumatoid arthritis though. | | | | to look for all three of these RFs. A note of |
| Patients with early RA can be negative for rheumatoid | | | | caution...most laboratories only look for IgM rheumatoid |
| factor. Between 10 and 20% of patients will be | | | | factor. Make sure your rheumatologist looks for all |
| persistently negative for rheumatoid factor throughout | | | | three. |
| their illness. However, between 80-90% of patients | | | | |