Performance characteristics of rapid (30-second) prescreening. Implications for calculating the false-negative rate...

Rapid (30-second) prescreening of cervicovaginal smears can be used to detect false-negative cases and determine the false-negative rate of primary screening, but the performance characteristics have not been evaluated fully. A test set of 242 cases including 80 originally false-negative cases were rapidly screened by 4 different cytotechnologists on 2 occasions. Intraobserver and interobserver reproducibility were good. Median specificity for each round of observations was 89% (range, 30%-96%). Median sensitivity for all true-positive cases was 78% (range, 63%-97%); for all false-negative cases it was 59% (range, 38%-89%). The relative sensitivity of rapid screening for true-positive and false-negative cases varied with the diagnosis. Rapid screening detected almost the same percentage of false-negative cases of atypical squamous cells of uncertain significance (ASCUS) as true-positive ASCUS cases (median ratio, 1.12; range, 0.72-1.52). The median ratio of false-negative to true-positive ASCUS cases was significantly different than the ratio for low-grade plus high-grade squamous intraepithelial lesions (0.68; range, 0.50-0.96). Although performance varies between individuals, in this test population the reproducibility, specificity, and sensitivity were good. Because it detects more false-negative cases at a lower cost per case than routine rescreening, rapid prescreening should be considered as an alternative to current quality control measures.