What is being tested?ESR is an indirect measure of the degree of
inflammation present in the body. It actually measures the rate of fall (sedimentation) of erythrocytes (red blood cells) in a tall, thin tube of blood. Results are reported as how many millimetres of clear plasma are present at the top of the column after one hour. Normally, red cells fall slowly, leaving little clear plasma. Increased blood levels of certain
proteins (such as fibrinogen or
immunoglobulins, which are increased in inflammation) cause the red blood cells to fall more rapidly, increasing the ESR.
