The effect of filtration on the loss of abnormal cervical cells in specimen preparation for automated cytology.

The UCLA monolayer procedure is used to produce a preparation of cervical epithelial cells for automated cytology. We investigated the nylon mesh filtration step of the procedure to determine if it altered the proportion of abnormal epithelial cells in the specimen. The proportion of such cells was found to be significantly lower (P less than 0.05) in the final specimen retained by a 10 micron nylon mesh filter than in the filtrate, which has been routinely discarded in our studies. The filtrate specimen is contaminated by large numbers of polymorphonuclear leukocytes, however, making it unusable for automated cytology at present. The implications of our findings for the cost effectiveness of classifier performance are considered, and the implications of the results for further improvements in specimen preparation are discussed.