Instrumentation for Automatically Prescreening Cytological Smears

Mass-screening application of the cytological smear for the detection of cervical cancer has been limited by a lack of technicians to screen the smears. By using an instrument to identify automatically those smears which are clearly negative, the effectiveness of the technician could be greatly increased. A quantitative analysis of a large number of smears showed that positive smears usually had a small number of cells with abnormally large and intensely stained nuclei that did not appear on negative smears. On the basis of this analysis, an experimental instrument-called the Cytoanalyzer-has been constructed. The Cytoanalyzer scans a smear, measures the size and light absorption of approximately 10,000 cells on the smear, classifies each cell normal or abnormal according to its nucleus size and absorption, and totals the number of cells falling into each classification. The smear is then classified normal or abnormal depending on the fraction of cells having abnormal characteristics. Preliminary tests with the Cytoanalyzer have been very promising. In a test of approximately 1000 smears, 65 per cent of the premenopause smears and 35 per cent of the postmenopause smears were properly identified. Plans are now underway to make a more thorough test of the screening capabilities of the instrument. If the test is successful, development of a clinical instrument will be started.