A blood smear is examined for:
- Red cells: Morphology, immature forms, inclusion bodies, arrangement of cells.
- White cells: Differential count, abnormal or immature forms.
- Platelets: Adequacy, abnormal forms.
- Parasites: Malaria, filaria.
A peripheral blood smear has three parts: Head, body, and tail. Also read: PREPARATION OF BLOOD SMEAR BY WEDGE METHOD.
A blood smear should be examined in an orderly manner. Initially, blood smear should be observed under low power objective (10×) to assess whether the film is properly spread and stained, to assess cell distribution, and to select an area for examination of blood cells. Best morphologic details are seen in the area where red cells are just touching one another. Low power view is also helpful for the identification of Rouleaux formation, autoagglutination of red cells, and microfilaria. High power objective (45×) is suitable for examination of red cell morphology and for differential leukocyte count. A rough estimate of total leukocyte count can be obtained which also serves to crosscheck the total leukocyte count done by manual counting or automated method. Oil-immersion objective (100×) is used for more detailed examination of any abnormal cells.
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