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.

Microscopic view of red blood cells.