What is Erythrocyte Sedimentation Rate?
The erythrocyte sedimentation rate measures the distance red cells fall in a vertical column of anticoagulated whole blood over one hour. The rate is governed largely by plasma proteins, especially fibrinogen and immunoglobulins, which reduce the negative surface charge on erythrocytes and promote rouleaux formation, causing cells to settle faster. It is therefore an indirect, slow-responding indicator of the acute-phase response, rising and falling over days rather than hours.