Description
Rheumatoid factor is used to help diagnose Rheumatoid Arthritis. It is eventually present in significant concentrations in about 80% of patients with RA but also present in other conditions and in a small percentage of healthy people.
Its concentration is measured by means of analysis of a blood sample drawn from the vein in the arm.
Purpose of the test
The goals with testing are to help diagnose rheumatoid arthritis, to distinguish it from other forms of arthritis and conditions with similar symptoms, and to evaluate its severity. Testing can be used to monitor the condition, its potential complications, response to treatment, and to monitor for potential side effects associated with some treatments.
There is no single test that can be used to diagnose rheumatoid arthritis; it is a diagnosis that is made through clinical evaluation with the assistance of laboratory and non-laboratory testing.
Laboratory Tests
- Rheumatoid factor - used to help diagnose RA.
- Erythrocyte sedimentation rate - this test (sed rate or ESR) shows the presence of inflammation in the body and the activity of the disease
- Cyclic Citrullinated Peptide Antibody (CCP) - a relatively new test that may be used to help diagnose RA, especially early in the disease and in patients who are RF negative.
- Erythrocyte sedimentation rate (ESR) - this test shows the presence of inflammation in the body and the activity of the disease. It is used to help diagnose RA and to evaluate and monitor the condition. ESR will be increased in RA but not in osteoarthritis.
- C-reactive protein test (CRP) - this test also indicates inflammation and tests for the activity of the disease. It may be used to help diagnose RA and to evaluate and monitor the condition. An increased level of CRP occurs in RA but not in osteoarthritis.
- Complete Blood Count (CBC) - this is a group of tests that are used to help evaluate the patient's red and white blood cells and hemoglobin to help evaluate and monitor the condition and complications such as anemia and/or a decreased white blood cell count.
- Comprehensive Metabolic Panel (CMP) - this is a group of tests that may be used to help evaluate and monitor the patient's kidney and liver function.
Non-Laboratory Tests
- American Rheumatism Association criteria, including: morning stiffness, arthritis in at least 3 joint areas, arthritis in hand joints, symmetric arthritis, rheumatoid nodules, rheumatoid factor, and radiographic changes are used to help diagnose RA. (A diagnosis of RA is considered in a person who has had at least four of these criteria for several weeks).
- X-ray - used to help diagnose RA and monitor joint damage but will not usually show significant changes early in the disease.
- Ultrasound and MRI - being used primarily as research tools to attempt to detect changes in the joints earlier in the disease.
Reference range values
0-14 IU/mL
Abnormal findings
RA Factor above the reference ranges are normally related with Rheumatoid Arthritis process, but it is also significantly present in other conditions and in a small percentage of healthy people.