The haematocrit is a blood value that exclusively reflects the cellular components (more precisely the number of erythrocytes) of the blood. In general, blood consists of a liquid component, the blood plasma and many different cells. As mentioned above, these cells are summarized as hematocrit (abbreviation Hkt), whereby the value actually only refers to the erythrocytes.
However, since more than 95% of the cellular portion of human blood consists of erythrocytes, i.e. cells that are responsible for distributing our oxygen throughout the body via blood, the hematocrit value is defined as the cellular blood value. The remaining 5% of the cell content in the blood consists of the blood platelets (thrombocytes), the cells of the acquired immune defense (lymphocytes) and the cells of the innate immune defense (leukocytes and monocytes). The hematocrit value is given in both the small and large blood count and is an important parameter to describe the composition of our blood and can also indirectly indicate anemia.
Determination of the hematocrit
The haematocrit value is always given as part of a blood count. In order to determine the hematocrit value, blood must be taken from the patient. It is not important whether the patient is fasting (i.e. has not eaten or drunk anything) or whether the patient has eaten food.
In order to obtain only the cellular parts of the blood, the blood must be placed in a centrifuge where, due to gravity, the cellular parts (i.e. the erythrocytes) move downwards while the liquid blood plasma remains on the surface. Thus, it is already possible to see with the naked eye where exactly the boundary between the cellular blood fraction (hematocrit) and blood plasma is located. For a more precise measurement, however, a so-called blood smear is then taken to determine the number of individual cells. Since the blood must not clump (clot) beforehand, which would automatically happen in the air outside the body, the anti-coagulant EDTA or heparin must be added to the blood beforehand.