Blood Smears Evaluation in Veterinary Haematology

Blood Smearing Procedure

• A drop of blood is placed on the end of a slide to create a thin layer for smearing.
• The spreader slide is placed at an angle of about 30 degrees in front of the blood spot to achieve a smooth, even smearing of the blood.

Staining Blood Smears

• Eosin, an anionic/acidic dye, is used in staining blood smears.
• The smear should extend about two-thirds of the length of the slide to allow for optimal evaluation.

Preparation and Evaluation

• The smear should be allowed to fully air dry prior to staining to prevent smudging or mixing of the stain with the blood.
• The best part of a blood smear for evaluation is the "feathered edge" where the blood cells are evenly dispersed and thinly spread.

Blood Smear Characteristics

• Anisocytosis refers to variation in erythrocyte diameter in stained blood smears.
• Polychromatophilic erythrocytes indicate an increased production of red blood cells.
• Reticulocytosis refers to the presence of reticulocytes in a blood smear.
• Microcytosis indicates small red blood cell size.
• Hypochromia refers to RBCs with poor hemoglobin concentration, characterized by centrally stained cells with a central pallor.

Staining Procedure

• A fixative (methanol) is used to fix the blood cells in place before staining.
• Diff-Quik solution 1 is used to stain the blood smear, allowing for visualization of blood cell morphology.

Blood Smearing Techniques

• The spreader slide should not be lifted until the feathered edge is completely formed to prevent uneven smudging.
• An uneven feathered edge and a smear that extends beyond two-thirds of the length of the slide indicate poor smearing technique.
• Harvesting a blood sample using a microhaematocrit tube allows for a more accurate representation of blood cell morphology.

This quiz covers the evaluation and analysis of blood smears, including the staining process and its importance in veterinary haematology. It discusses the use of Romanowsky stains, such as Diff-Quick, for rapid staining and differentiation of smears.