Erythrocyte sedimentation rate (ESR or sed rate) is a test that indirectly measures the degree of inflammation present in the body. The test actually measures the rate of fall (sedimentation) of erythrocytes (red blood cells) in a sample of blood that has been placed into a tall, thin, vertical tube. Results are reported as the millimeters of clear fluid (plasma) that are present at the top portion of the tube after one hour.
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