Effect of the special properties of monolayer cell preparations for automated cervical cytology on visual evaluation and classification. With an estimation of the number of cells required to be screened.

Monolayer preparations used in cell image analysis show some peculiarities as compared with conventional cytologic smears, such as homogeneous distribution of cells, distinct appearance of cells and a reduced number of background elements. However, for use in gynecologic cytology, monolayer preparations must be accessible to visual examination and classification. To investigate the consequences of the special features of these preparations on the strategy of visual evaluation, we estimated the minimum number of cells needed for a diagnostic decision. Cell counts were made of gynecologic monolayer preparations from 50 women with no suspicion of malignancy and 50 women with invasive squamous-cell carcinoma of the uterine cervix and its precursors. Our results showed that the more serious the lesion, the lower the number of cells needed for a diagnostic decision. The highest mean values of numbers of cells needed for an effective diagnosis were estimated in cases of mild and moderate dysplasia (734 cells) and in non-suspicious cases (731 cells). The number of cells needed did not exceed 1,700 in any case. The false-negative and false-positive rates were 6% and 2%, respectively, including the cases of mild to moderate dysplasia.