The significance of random sample size in flow-through photometric prescreening in cervical cytology.

The determination of nuclear DNA content by flow-through photometry is employed as a prescreening procedure in cervical cytology. The goal of a prescreening procedure is to obtain the smallest possible number of false negative findings with an economically acceptable number of false positive findings, which must be retested. False negative findings result from the often low relative frequency of atypical cells in a mixed population of normal and atypical cells. Only between 10,000 and 50,000 cells are contained in a random sample from the total suspended smear material. It was the purpose of this study to investigate whether a flow-through photometric study of the entire suspension and thus the larger absolute frequency of atypical cells mught lead to a decrease in false negative results. Flow-through photometric evaluation of the entire smear material is not superior to measurement of a random sample of 10,000-50,000 cells. 1. The relative frequency of atypical cells is unchanged, and thus also the proportion of false negative findings. 2. The number of false positive findings increases by 10% due to the inclusion of aggregates at the bottom of the preparation. 3. The measuring time is increased 10-fold, thus making the prescreening procedure uneconomical.