This document discusses packed cell volume (PCV), also known as hematocrit. PCV is defined as the percentage of red blood cells in a blood sample after centrifugation. It is determined by centrifuging anticoagulated whole blood in a specialized tube called a Wintrobe tube. This packs the red blood cells to the bottom, allowing measurement of the percentage of total blood volume occupied by red cells. PCV is an indicator of anemia, dehydration, or other blood conditions and is measured using several methods including the macro Wintrobe tube method or microcapillary tube method.