Erythrocyte Sedimentation Rate Test (ESR) Definition

Erythrocyte sedimentation rate test (ESR) is a test that screens for inflammation. The faster red blood cells (erythrocytes) fall to the bottom of a tube filled with the patient’s blood, the greater the degree of inflammation. Inflammation is a factor in many conditions, and a positive ESR test can support the diagnosis of an inflammatory condition. An ESR test can also be used to see how active the condition is.