Thionine-Feulgen-Congo red staining of cervical smears for the BioPEPR image-analysis system

A staining method developed for use with BioPEPR (Biological Precision Encoding and Pattern Recognition), an automated image-analysis system for cervical smears, is described. The stain is a combination of the Feulgen procedure, with thionine-SO2 as the Schiff reagent, and Congo red, which is used as a counterstain. The stain resulted in smears suitable both for microscopic diagnosis and for BioPEPR measurements made on photonegatives at a single wavelength 545 nm. A high level of reproducibility and accuracy of nuclear and cytoplasmic area measurements was obtained. Nuclear integrated optical density could be well measured and was shown to be useful in discriminating between normal and abnormal cells. Using a combination of morphologic features, a high level of cell classification accuracy was reached. The possibility of using the stain for more detailed studies is discussed.