"I am convinced that the findings of this study are extremely important in understanding the biology of the false negative Pap smear," Felix says. "Never before have we seen such clear evidence that barriers to exfoliation are linked to false negative Pap smears." The team conducted the study with tissue samples from 25 women known to have cervical dysplasia (aberrant cells preceding cancer). Researchers analyzed whether the tissue samples showed normal distribution of E-cadherin, and then compared each tissue sample to its corresponding Pap smear result.

Of the 25 women, 12 had had a normal Pap smear. All 12 of these women, however, had a positive result through speculoscopy with PapSure. PapSure is a testing system that includes a special light used during the pelvic examination, allowing physicians to actually see suspicious lesions on the cervix.

The remaining 13 women had abnormal Pap smears. Researchers were able to analyze E-cadherin distribution in 10 of these samples. Eight of 10 of these samples showed normal distribution of E-cadherin.

In contrast, of the 12 women with false negative Pap smears, 10 of 11 samples that could be examined showed the abnormal presence of E-cadherin in the superficial layers of the cervix.

"Of the patients with known cervical abnormalities who had normal Pap smears, 91 percent had an abnormal distribution of the E-cadherin adhesion molecule," Felix says. Felix cautions, however, that larger studies with randomly selected patients are needed to verify the findings. Other adhesion molecules also may be involved in the process.

Possible alternative reasons for false-negative Pap smears include poor cell sample collection, mistakes in transferring cells to slides and human error in evaluating the collected cells.

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Contact: Jon Weiner
Jonweine@usc.edu
323-442-2830
University of Southern California
24-Jun-2002