An erythrocyte sedimentation rate is a blood test used for monitoring or detecting inflammation, explains eMedicineHealth. The test measures how rapidly erythrocytes or red blood cells drop to the bottom of a test tube. A rapid fall is indicative of inflammation in the body.
Red blood cells have a tendency of clumping together when inflammation is present in the body, reports eMedicineHealth. When red blood cells stick together, density increases, which causes them to fall more rapidly in a test tube suspension. This drop or sedimentation rate is recorded in millimeters over the course of one hour. Sedimentation rates are not a stand-alone diagnostic tool, but are used by doctors in conjunction with other test results and the patient's symptoms. A sedimentation rate test is useful in monitoring inflammatory diseases such as rheumatoid arthritis and lupus.