FALSE NEGATIVES IN FOCUSED RESCREENING OF PAPANICOLAOU SMEARS - HOW FREQUENTLY ARE ABNORMAL-CELLS DETECTED IN RETROSPECTIVE REVIEW OF SMEARS PRECEDING CANCER OR HIGH-GRADE INTRAEPITHELIAL NEOPLASIA

The 5-year retrospective rescreening process is an integral part of th e cytology laboratory's quality assurance program. Its major role is t he identification of errors in screening and/or interpretation that re present rare events and patterns. Recognition of such errors can provi de for reorientation and reeducation of cytology personnel, ultimately to improve prospective accuracy. Careful research studies have shown that retrospective rescreening may identify abnormalities on slides di agnosed as negative in more than 50% of cases analyzed. Surveys of act ual clinical laboratory programs show detection of abnormalities in si gnificantly lower percentages, generally in the range of 10% to 30%. T he majority of cases identified are reclassified in the category of at ypical squamous cells of undetermined significance. Cases of identifie d high-grade squamous intraepithelial lesion are identified as a minor ity of cases in virtually all laboratories surveyed. In the cases reas sessed as high-grade squamous intraepithelial lesion, a common cytolog ic pattern is that of a few isolated, small, ''immature metaplastic,'' dysplastic cells being present.