What is it about ?
A blood smear is a special examination of the blood, under a microscope. The blood is obtained by a classic blood test or by a prick in the finger. A drop of blood is spread on a glass slide, dried, and then stained with a special stain. This is then analyzed under a microscope by a lab technician or doctor.
There are machines that count the number of red blood cells, white blood cells and platelets in the blood (this is called automatic counting). If the number of cells is abnormally low or high, without immediate explanation, then a blood smear is taken. It can check whether the shape of cells is normal or not. This is how the doctor can make a diagnosis. In other cases, automatic blood cell and platelet counting is normal, but checking the cell shape can still be helpful and aid in the diagnosis.
Examples of conditions in which the blood cells have particular abnormal shapes:
- The sickle cell anemia ; It is an inherited disease in which the red blood cells have a crescent shape; they are therefore called sickle cells (= crescent shaped). They can therefore no longer carry as much oxygen as normal red blood cells. Sickle cells are visible on a blood smear.
- A deficiency of vitamin B12 or folic acid ; We can see on the smear that the nuclei of white blood cells have several lobes.
- A hairy cell leukemia; OThere can be special white blood cells on the smear that appear to be covered with tiny hairs.
Examples of conditions with too high a number of certain blood cells:
- The chronic lymphoid leukemia : There are too many lymphocytes, a type of white blood cell.
- Some allergic conditions : There are too many eosinophils, another type of white blood cell involved in allergy.
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