Papanicolaous solution EA50 (PAP 3b) is one of the staining components used in Papanicolaou staining (PAP staining). PAP staining is a multi-step staining technique used primarily in the cytological examination of cells in body fluids, especially for cervical smears in gynecological cytology.
EA50 is a mixture of eosin Y and various azure dyes called the eosin-azure combination. It is used in the third step of PAP staining after the nuclei are stained with Papanicolaous Hematoxylin (PAP 1a or PAP 1b) and the cytoplasm is stained with Orange G (PAP 2a). The EA50 solution stains the cytoplasm and various cytoplasmic structures in different colors, providing differential staining that facilitates detailed examination of cell morphology and diagnosis of cell changes or abnormalities.