The American Cancer Society estimates that about 11,150 cases of cervical cancer will be diagnosed this year. However, the survival rate for this disease is very high if changes in the cervix are detected early. The conventional screening method involves taking a sample of cervical cells and smearing them on a glass slide for examination. A newer approach involves producing a suspension of cells by rinsing the collection instrument with liquid; this mixture is taken to the laboratory for computerized analysis.

The liquid-based approach provides faster reading times and also allows cytologists to perform additional testing, such as for the human papillomavirus (HPV). However, not much is known about the accuracy of this method in comparison with the standard one.

Elizabeth Davey and her colleagues from the School of Public Health at the University of Sydney in Australia evaluated the accuracy of a liquid-based computerized image analysis system compared with the conventional glass slide method.

As reported in the August issue of the British Medical Journal, samples were taken from 55,164 women and examined using both methods. For the liquid-based approach, the researchers used the ThinPrep Imager from Cytyc Corp. of Marlborough, Mass. The imager scanned each slide and measured the integrated optical density of each cell’s nucleus. Using a special algorithm, it then identified 22 fields of interest that were most likely to contain abnormal cells. A cytologist read the slides using the system’s microscope with 10× and 40× objectives.

The researchers found that the computerized imager identified 1.4 percent more cytological abnormalities than the conventional method (7.4 percent overall for the imager and 6.0 percent overall for the conventional method). It also detected 71 more cases of histologically proven high-grade cervical abnormalities (from 170 more biopsies) than did conventional cytology. The system also resulted in fewer unsatisfactory slides (1.8 percent) compared with conventional cytology (3.1 percent).

The researchers conclude that the liquid-based method using the computerized imaging system could help detect more abnormalities and improve screening for women.