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Blood Tests to Diagnose Arthritis

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If your doctor suspects you have arthritis, he or she may have your blood drawn to determine which type of arthritis you have. In people with osteoarthritis, blood tests are not usually abnormal, but with other types of arthritis, including rheumatoid arthritis, certain tests will help with a proper diagnosis.

Here is a review of the different types of blood tests and markers used to diagnose arthritis and other inflammatory conditions.

What Blood Markers Are Used to Diagnose Rheumatoid Arthritis?

Rheumatoid factors are a variety of antibodies that are present in 70% to 90% of people with rheumatoid arthritis (RA). Rheumatoid factor (RF), however, can be found in people without RA or with other autoimmune disorders. In general, when no rheumatoid factor is present in someone with RA, the course of the disease is less severe.

A new test for rheumatoid arthritis that measures levels of antibodies that bind citrulline modified proteins (anti-CCP) is more specific and tends to be elevated in patients with rheumatoid arthritis or in those about to develop rheumatoid arthritis. The presence of anti-CCP antibodies can be used to predict which patients will get more severe rheumatoid arthritis.

Are There Tests to Determine Inflammation?

Yes. The erythrocyte sedimentation rate (ESR) reflects the degree of inflammation in the body. In healthy people, the ESR is low and it climbs with inflammation. It doesn't point to any particular disease, but is a general indication of the amount of inflammation in the body. In lupus and polymyalgia rheumatica, the ESR often correlates with disease activity.

C-reactive protein (CRP) levels are an even better indication than ESR of the amount of inflammation present. In people with rheumatoid arthritis, if the CRP is high, it suggests that there is significant inflammation or injury in the body.

Both CRP and ESR levels are used to monitor disease activity and to monitor how well someone is responding to treatment.

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