Image analysis and DNA content of urothelial cells infected with human polyomavirus

Human polyomavirus (HPV)-infected cells in the urinary sediment are characterized by large homogeneous basophilic nuclear inclusions, which may mimic the nuclear changes in urothelial cancer. The virus is composed of double-stranded DNA and produces intense green fluorescence of nuclei stained with acridine orange. DNA measurements of Feulgen-stained smears of urinary sediment disclosed that HPV-infected cells have aneuploid DNA values and could not be differentiated from cancer cells on the basis of DNA content alone. On the other hand, computer discriminant analysis performed on high-resolution images of HPV-infected and malignant urothelial cells stained by both the Papanicolaou and Feulgen methods showed that excellent discrimination between the two groups of cells could be achieved with either stain. The misclassification rates ranged from 3% to 9%. This differentiation was almost entirely based upon computer features pertaining to the texture of the nuclear chromatin. This study documented still further the diagnostic value of high-resolution image analysis of cells in the human urinary sediment.