Various blood tests may be used to help diagnose RA, determine its severity, and detect complications of the disease.
Rheumatoid Factor. In RA, antibodies in the blood that collect in the synovium of the joint are known as rheumatoid factor. In about 80% of cases of RA, blood tests reveal rheumatoid factor. It can also show up in blood tests of people with other diseases. However, when it appears in patients with arthritic pain on both sides of the body, it is a strong indicator of RA. The presence of rheumatoid factor plus evidence of bone damage on x-rays also suggests a significant chance for progressive joint damage.
Erythrocyte Sedimentation Rate. An erythrocyte sedimentation rate (ESR or SED rate) measures how fast red blood cells (erythrocytes) fall to the bottom of a fine glass tube that is filled with the patient’s blood. The higher the sed rate the greater the inflammation. Because the sed rate can be high in many conditions ranging from infection to inflammation to tumors, the ESR test is used not for diagnosis but to help determine how active the condition is.
C-Reactive Protein. High levels of C-reactive protein (CRP) are also indicators of active inflammation. Like the ESR, a high result does not indicate what part of the body is inflamed, or what is causing the inflammation.
CCP Antibody Test. The presence of antibodies to cyclic citrullinated peptides (CCP) can identify RA years before symptoms develop. In combination with the test for rheumatoid factor, the CCP antibody test is the best predictor of which patients will go on to develop severe RA.
Tests for Anemia. Anemia is a common complication. Blood tests determine the amount of red blood cells (hemoglobin and hematocrit) and iron in the blood. If Anemia is diagnosed in an RA patient, it is important to investigate whether it is due to iron deficiency in the nutrition or inflammation.
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