EA 31 Pap 3A reagent is an alcoholic solution of two acid dyes, Eosin Y and Light Green SF, with added phosphotungstic acid (PTA). The first step in using the Papanicolaou staining method implies nuclear staining with a hematoxylin solution, and next two steps consist of counterstaining using the monochromatic OG-6 reagent and one of the polychromatic EA reagent formulations. The Orange G molecule stains the cytoplasm, and in later stages of the procedure it remains only in the mature, keratinized cells. The third step consists of using of one of the polychromatic EA solutions that stains the unstained cellular components, such as squamous cells, nucleoli, cilia, and erythrocytes. Test samples can be gynecological and non-gynecological, such as sputum, urine, and cytological puncture samples. In order to obtain optimal staining results, EA 31 Pap 3A reagent has properties completely in compliance with other BioGnost’s reagents for cytological smearing acc. to Papanicolaou – Hematoxylin HP, Pap 1A reagent and OG-6, Pap 2A reagent.