The Blood Smear
All about a blood smear
As part of a minimum data basis we collect a small drop of blood from the pets ear. This is done by using a needle to prick the tip of the ear, a drop will be collected on a microscopic side and another slide will be used to spread the drop.
The aim of spreading the drop is to get a single layer of cells to be able to evaluate the size, shape, colour and amount of cells.
This slide will be stained with Romanowsky- stain and then placed under the microscope. This is where the investigation begins.
What do we look at?
There are 3 big groups of cells:
- Red blood cells
- White blood cells
Each group of cells has a different function and help the veterinarian to make a diagnosis.
The red blood cells will be looked at first. The red blood cell is the cell that carries oxygen to the body. The size, shape, colour, inclusions and number can tell us if the pet is anemic (low blood count), it can tell is if the body is responding and making new red cells (regenerative) or not responding (non-regenerative). This can aid the veterenarian in making a list of possible causes that can be as easy as iron deficiency to something as complex as an autoimmune disease. Some morphological changes can even tell us if a pet has been intoxicated!
The next group is the white blood cells. This group has many members and each has its own function, but the basics of this group is to protect the body against infection. If we have an increase in these cells it can mean an infection is brewing or inflammation is present in the body and the body is fighting, but if we have to few numbers it means the body is losing the fight against some infection and this can be life threatening.
Then we have the platelet. The smallest cell of the 3 groups. This little cell is the reason we don’t bleed to death. It forms clots. Some parasitic infections and autoimmune diseases causes a decrease in the platelet numbers. While endocrine diseases can cause in increase.
While looking at a blood smear we don’t always just look at cells, we look for parasites too. Babesia is a tick-born parasite that lives in the red blood cell, Ehrlichia is another tick born parasite and can be found in white blood cells.
The blood smear is a valuable tool in the investigation of any ill patient. While we can estimate numbers, to quantify cell numbers we collect a tube of blood from the animals vein and put it through a machine that counts the actual numbers.