Haematocrit

Part of speech: noun

Definitions

1. The percentage of the total blood volume made up of red blood cells, commonly measured in a blood test to assess anemia or dehydration
2. The share of whole blood that consists of red cells, expressed as a percentage and used clinically to evaluate oxygen-carrying capacity
3. A laboratory measure showing how much of a blood sample is composed of erythrocytes, reported as a proportion of the total volume

Etymology: Magnus Blix, a Swedish physiologist, coined this term in 1891 for the proportion of blood made up of red cells. The name is a deliberate compound: "hemato-", from Greek "haima" meaning blood, joined to "krites", meaning judge or umpire. Blix was judging the blood, sorting it into its parts. The literal sense of the Greek element is "one who separates" or "decides", and the scientific use is closer to that idea than the English word "judge" suggests. A centrifuge spins a sample of blood so that the heavier red cells settle at the bottom, and the height of that red layer as a fraction of the whole sample gives the figure. The spelling "haematocrit" with the "ae" is an older variant of the now more common "hematocrit".

Synonyms: hematocrit, packed cell volume