Decreasing False-Negatives for Cervical Cancer


The traditional Pap smear - its full name is Papanicolaou - introduced some 50 years ago for the early detection of cervical cancer, generally leads to about 70% fewer deaths from cervical cancer. The Pap smear examines stained cells from the mucous membrane of the cervix for precancerous changes. However, it is estimated that one- third of women who die from cervical cancer do so because it was not accurately detected at an early enough stage for successful treatment.

A probable reason for this, according to the National Cancer Institute, is the fact that the Pap smear produces a high rate of false negatives - 20-40% of all abnormal tests. According to the medical journal Acta Cytologica, the error rate for cervical cancer may be 50%. A false negative tells the patient and doctor that there are no signs of cervical cancer; yet, some time later, the woman develops cervical cancer.

The evidence was there all along, but could not be picked up by the Pap smear. This may be because, although it registers between 50,000 - 300,000 cells in a single smear from the cervix, abnormality indicating potential cancer may be limited to dozen or fewer cells. Identifying these few cells amidst many thousands is a formidable task.

A screening procedure developed in the late 1980s, called PAPNET Testing, has been shown to identify and display abnormal or cancerous cells in 97% of abnormal cases, thus dramatically reducing the error rate of false negatives and potentially saving lives by accurate early detection.

Using an automated microscope, a full-color camera, and a high-speed image- processing computer, the PAPNET system meticulously screens slides for evidence of abnormalities. Once abnormal individual cells or cell clusters have been pinpointed from a single Pap smear, their images are stored in the computer; when the entire Pap smear has been rescreened, the 128 "cell scenes" judged as most significant by the PAPNET computer are selected for visual evaluation by trained technicians.

Researchers at the University of California at Los Angeles proved that PAPNET is more accurate at reclassifying potential positive Pap smears than manual, visual evaluation. When lab technicians studied 62 Pap smears by standard manual methods, this resulted in 31% of negatives being reclassified as needing further review; but PAPNET reclassified 83%, of which about one half turned out to be abnormal.

Dorothy L. Rosenthal, M.D., and colleagues reported in Acta Cytologica that not only can PAPNET reduce screening errors, but it can save the lives of patients. In another study, PAPNET picked up 72 cases of cervical abnormalities in 228 women who had been told their Pap tests were negative.

To date, PAPNET has been applied to 400,000 Pap smears in laboratories in 15 countries; in the U.S., at least 100 laboratories use the Papnet system and charge an average of only $40 per rescreening.

(Reprint, Alternative Medicine Digest, Issue 14)

Copyright © 1996. The Light Party.

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