Field Stain

Field stain is a histological method for staining of blood smears. It is used for staining thick blood films in order to discover malarial parasites. Field’s stain is a version of a Romanowsky stain, used for rapid processing of the specimens.

Principle:

• Field’s stains contain methylene blue and eosin.
• These basic and acidic dyes induce several colours when applied to cells.
• The fixator, methanol, does not allow any additional changes to the slide.
• The basic component of peripheral white blood cell( cytoplasm) is stained with acid dye and described as eosinophil or acidophil.
• The acid component that is nucleic acid of the nucleus takes on the basic dye and is stain blue to violet  called basophil.
• The neutral components of the cells are stained by both dyes(Field’s stain A and B solution)

Somposition:

Field’s Stain A

Methylene blue	1.300 gram
Potassium phosphate	6.250 gram
Disodium hydrogen phosphate	5.000 gram
Fresh distilled water	550.000 ml

Field’s Stain B

Eosin	1.300 gram
Disodium hydrogen phosphate	5.000 gram
Potassium dihydrogen phosphate	6.250 gram
Distilled water	500.000 ml

• Field’s stain A has is a dark violet coloured solution
• Field’s stain B has is an orange coloured solution

Procedure:

1. Place a drop of blood on a slide and spread it over an area of about 1 cm2.( The film should be distributed so thinly that it appears transparent.
2. Allow the film to air dry (Do not fix the slide)
3. Flood or dip the slide in Field’s Stain A for 2-3 seconds.
4. Wash or rinse the slide with distilled water (Agitate gently)
5. Flood or dip the slide in Field’s Stain B for 2-3 seconds and wash with distilled water.
6. Now air dry  the smear or slide and observe under microscope.

Results:

Neutrophil granules	lilac
Eosinophilic granules	orange
Red cells	pink
Nuclei	blue
Malaria parasites	deep red chromatin and pale blue cytoplasm.
Leucocyte	purple nuclei and pale blue background
Red cells are lysed	only background stroma remains.

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