A sedimentation rate is a blood test that is commonly performed on patients with RA. This test is also sometimes referred to as a “sed rate” or an erythrocyte sedimentation rate (ESR). The sedimentation rate measures how fast the red blood cells (erythrocytes) settle (become sediment) in the bottom of a glass tube.
Erythrocyte sedimentation rate (ESR)
A diagnostic test for inflammatory diseases that measures the rate at which red blood cells settle out from a well-mixed specimen of blood.
RA is characterized by inflammation of the joints and other tissues. When inflammation occurs, the body produces many proteins that help fight infection and repair injured tissues. The more inflammation the body experiences, the more proteins it produces. These extra proteins cause the red blood cells to settle faster in the bottom of a glass tube. Therefore, it can be inferred that the more rapidly the red blood cells drop, the more inflammation (that is, RA) is present in the body. The sed rate tends to reflect the clinical disease activity and to parallel such symptoms as morning stiffness and fatigue. Joint examination by the physician is far more useful in assessing the amount of joint inflammation (called synovitis).
Synovitis
Inflammation of the synovium.
A sed rate is performed on a sample of blood. Blood is drawn from the patient's vein, usually from the inside of the elbow or the back of the hand. A small amount of anticoagulant is added to the blood sample to keep the blood cells from clotting. The blood cells are placed in a special glass tube that is calibrated with millimeter markings on the side, and the blood is allowed to settle for one hour. After the hour has elapsed, the level of the top of the red blood cell layer is measured and recorded. The normal sedimentation rate is 0 to 15 millimeters per hour for men and 0 to 20 millimeters per hour for women. In healthy people who are more than 60 years old, the normal sedimentation rate can be slightly elevated.
Effective treatment of RA will decrease the amount of inflammation and, therefore, lower the sed rate. A physician may check a patient's sed rate frequently to see whether the treatment is working successfully. Keep in mind that a normal sed rate doesn't mean that you are cured and no longer need treatment for RA.
A normal sedimentation rate doesn't mean that you are cured and no longer need treatment for RA.