Diagnosing Rheumatoid Arthritis
C-Reactive Protein (CRP) Test
A blood test called the sedimentation rate (sed rate) is a crude measure of the inflammation of the joints. The sed rate actually measures how fast red blood cells fall to the bottom of a test tube. The sed rate is usually faster (high) during disease flares and slower (low) during remissions. Another blood test that is used to measure the degree of inflammation present in the body is the C-reactive protein. Blood testing may also reveal anemia, since anemia is common in rheumatoid arthritis, particularly because of the chronic inflammation.
The rheumatoid factor, ANA, sed rate, and C-reactive protein tests can also be abnormal in other systemic autoimmune and inflammatory conditions. Therefore, abnormalities in these blood tests alone are not sufficient for a firm diagnosis of rheumatoid arthritis.