■ SMEAR: preparation of a sample blood smear
■ STAIN: preparation and staining of a sample blood smear
Smears are performed with a wedge, using the surface-tension effect of the blood and according to a user defined smearing profile.
Smearing wedge principles
The smearing profile consists of the following adjustable parameters:
May-Grünwald Giemsa protocol (MGG)
Polychromatic staining technique that uses two stains that consist of two components, one alkaline, the other acid:
They form a stabilized neutral solution which is inactivated by alcohol.
The first step in the staining operation is to fix the blood by using the alcohol contained in the pure May-Grünwald. The staining action begins when Buffer is added. The cell components are selectively stained according to their individual chemical composition:
Staining results depend on the level of acidity of the Buffer (more red when pH decreases, more blue when pH increases).
Wright stain is a polychromatic stain consisting of a mixture of eosin and methylene blue. When applied to blood cells, the dyes produce multiple colors based on the ionic charge of the stain and the various components of the cell.
The eosin ions are negatively charged and stain basic cell components an orange to pink color. The methylene blue ions are positively charged and stain the acid cell components in varying shades of blue.
The neutral components of the cell are stained by both components of the dye producing variable colors.