Staining a blood smear

There are several different common staining techniques such as Giemsa, Wright’s, and quick staining. Which technique is used can depend on the time available for analysis, the level of detail needed and the particular diagnosis that is being investigated; for example, Giemsa staining is often used to detect blood parasites such as Malaria.

Wright’s, Giemsa, and quick staining are all types of Romanowsky staining techniques. They all use eosin and methylene blue dyes. In each technique, these dyes are combined in a specific way to produce a spectrum of colors that allows for the differentiation of the blood components and their internal structures:

  • Eosin is an acidic dye that stains basic (or acidophilic) structures red or pink. In blood smears, it typically colors red blood cells and the granules in some types of white blood cells.

  • Methylene blue is a basic dye that stains acidic (or basophilic) structures blue. In blood smears, it mainly colors the DNA in white blood cell nuclei and certain granules in other types of white blood cells.

There are two blood smear images. The one on the left contains approximately one hundred red blood cells, which show a discoid shape and are stained bright red. There are also five lymphocytes, which are slightly larger cells with large, darkly stained nuclei that take up most of the cell's volume. The image on the right-hand side contains over one hundred red blood cells, which appear red and discoid in shape, but are more darkly stained. Likewise, the three white blood cells present stain purple but darker than in the Wright's stained blood smear.

Figure 1. Blood smears stained with Wright's (left) and Giemsa (right) stains.