A model for the classification of specimens containing random proportions of abnormal cells.

The effect of abnormal cell proportion on the performance of an automated cervical prescreening system is discussed in K.R. Castleman and B.S. White, Cytometry 2:155-18. The model employed assumes fixed proportions of abnormal cells, both in the design stage and in the test stage. In the present paper, an extended model is developed that allows for random variability of this proportion. It is shown, that there is a fundamental, non-zero lower limit to the false-negative specimen error rate, which depends only on the coefficient of variation. This limit may be reached even for moderate values of the coefficient of variation, which implies that a satisfactory prescreening system may not be feasible.