Thionine-Feulgen Congo Red -- a new staining technique for automated cytology

A new staining method has been developed for an automated pre-screening device for cervical smears called BioPEPR. The method is a combination of the Feulgen technique with thionine as th Schiff reagent, and congo red. Thionine and congo red have absorption maxima at 585 nm and 500 nm respectively. The staining results in cells with an orange-red cytoplasm and brownish-blue nucleus. These smears can e easily screened using a normal microscope. The BioPEPR system scans photonegatives of the smears that are made at a magnification of ten using monochromatic light of 545 nm. The staining facilitates good discrimination between background and cytoplasm and between cytoplasm and nucleus, allowing morphologic parameters such as cytoplasmic area, nuclear area and nuclear integrated darkness to be well measured.