Erythrocyte sedimentation rate

The erythrocyte sedimentation rate (ESR), also called a sedimentation rate, sed rate or 'Biernacki Reaction', is a non-specific measure of inflammation that is commonly used as a medical screening test.

To perform the test, anticoagulated blood is placed in an upright tube, known as a Westergren tube and the rate at which the red blood cells fall is measured and reported in mm/h.

When an inflammatory process is present, the high proportion of fibrinogen in the blood causes red blood cells to stick to each other. The red cells form stacks called 'rouleaux' which settle faster. Rouleau formation can also occur in association with some lymphoproliferative disorders in which one or more immunoglobulins are secreted in high amounts. Rouleau formation is however a physiological finding in some equidae and can be as such in felidae and suidae species, namely the horse, cat and pig respectively.

The ESR is increased by any cause or focus of inflammation. The ESR is decreased in sickle cell anemia, polycythemia, and congestive heart failure. The basal ESR is slightly higher in females.