The Pap smear is the most successful cancer screening tool ever developed. The goal of the Pap smear is to discover abnormal cells or cells that may develop into cancer. No screening tool is more effective than the Pap smear for detecting abnormalities of the cervix.
Every screening test has an error rate.
This could happen because the location of the abnormality on the cervix could not be reached by the sampling device or the cells did not get transferred from the sampling device to the slide. The number of abnormal cells may be very small and the laboratory did not see them. The abnormal cells may be confused for normal cells by the laboratory. A false positive result may happen when laboratory personnel think normal cells are abnormal. The best way to protect yourself against false negative results is to have regular gynecological examinations including a Pap smear.