Question: What is erythrocyte sedimentation rate (sed rate) and how is it used to diagnose rheumatoid arthritis?
Answer: The erythrocyte sedimentation rate -- or sed rate sometimes as it's called -- is a measure of inflammation in the body. It's a laboratory test that measures certain proteins that are present in the blood that reflect inflammation in the body. It's not a very specific test, so it measures inflammation from a variety of different causes and a variety of different sources.
In rheumatoid arthritis however, the sed rate is typically elevated, reflecting the inflammation from the disease. Rheumatoid arthritis is a disease not just of the joints, but of the whole body. And so patients who have rheumatoid arthritis have systemic inflammation throughout their whole body, and the sed rate is a marker for this.
So the sed rate can be used to identify how severely affected a patient is early on in the course of their arthritis, and also can be used as a way to follow the course of therapy. As patients are treated appropriately and the disease improves, the sed rate level should go down, and that can be a marker of response to treatment.
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