EFO_0004348 (hematocrit) is the volume of packed RED BLOOD CELLS in a blood specimen. The volume is measured by centrifugation in a tube with graduated markings, or with automated blood cell counters. It is an indicator of erythrocyte status in disease. For example, ANEMIA shows a low value; POLYCYTHEMIA, a high value. Also known as: Ht, packed erythrocyte volume, packed red-cell volume.