What is Erythrocyte Sedimentation Rate?
The erythrocyte sedimentation rate measures how far red cells fall through a column of anticoagulated whole blood in one hour. Sedimentation depends on rouleaux formation — the stacking of red cells — which is promoted by asymmetric plasma proteins, principally fibrinogen and to a lesser extent immunoglobulins. Inflammation raises fibrinogen through the acute-phase response, increasing rouleaux and accelerating the fall. Because it depends on hepatic fibrinogen synthesis, ESR rises slowly over 24 to 48 hours and falls slowly over days to weeks, and because it depends on red cell mass and morphology it is directly influenced by haematocrit and red cell shape.