Wrightstain

Wright stain is a polychromatic Romanowsky-type stain used to differentiate and identify cells in peripheral blood smears and bone marrow aspirates. It was introduced by James Homer Wright in the early 20th century and remains a standard hematology stain. In many laboratories it is used alone or as part of Wright-Giemsa staining.

Composition and mechanism: The stain is a mixture of an acidic dye (eosin Y) and a basic dye (methylene blue, with azure components in some formulations) in a buffered methanol solution. When applied to fixed slides, eosin stains cytoplasmic components pink to orange, while the basic dyes stain nuclei and granules blue to purple. The result is differential staining of erythrocytes, leukocytes, platelets, and intracellular structures, enabling identification of cell types and abnormalities.

Procedure: Smears are fixed briefly in methanol, stained with the Wright solution for a short period, then washed with buffer and water and allowed to air-dry before examination.

Applications: Wright stain is used for routine evaluation of peripheral blood morphology and for differential white cell counts. It helps identify abnormal cells such as blasts and dysplastic features in bone marrow or blood. The stain can aid visualization of parasites or inclusions, though parasites are more commonly highlighted with complementary stains like Giemsa.

Limitations and notes: Accuracy depends on consistent pH, staining time, and stain freshness; variations can affect color intensity and differentiation. Standardization and quality control are important to minimize artefacts. The stain involves methanol, so standard laboratory safety practices apply.

History and variants: The method was developed by James H. Wright circa 1902. Wright-Giemsa is a widely used variant that combines Wright's stain with Giemsa to enhance differential differentiation of blood cells. Wright’s stain remains a foundational Romanowsky-type stain in hematology.