The effectiveness of cytological rescreening in the reduction of false negative/positive Pap reports

Cytological investigation of the cervix has proven to be a valuable tool in the early detection of cervical cancer; however, the high incidence of false negative or false positive smear reports is an important drawback.

To investigate retrospectively the value of partial rescreening methods as tools for improving the sensitivity and specificity of Pap test routine screening.

Out of a total of 4664 cervical samples examined by Pap test, 20% were randomly selected and rescreened with a more detailed examining protocol by the same cytologist; in addition, targeted rescreening of all samples with severe lesions was carried out.

During initial testing, 478 smears (10.24%) showed cytological abnormalities, classified as ASC-US (5.79%); L-SIL (3.32%) and H-SIL (1.14%). At random rescreening, a significant decrease in the number of negative smears (83.05% vs. 85.9%, p = 0.036) was recorded, together with an increase (7.68% vs. 5.79%, p = 0.043) in the number of smears classified as ASC-US. No significant differences were recorded for L-SIL or H-SIL samples. Retrospective targeted rescreening of all 208 samples initially diagnosed as L-SIL and H-SIL revealed 42 false positive results and 12 false negative ones. Errors were linked to suboptimal smear preparation: scant cellularity, material in clumps, paucity of abnormal cells, pale dyskarosis, small microbiopsy- like aggregates.

Partial random rescreening or targeted rescreening enables a better interpretation of suboptimal prepared smears. Targeted rescreening allows a correct detection of even low percentages of atypical cells. Other confounding factors, such as the laboratory workload and the regional prevalence of the disease, can exert an important effect on the correct classification of cytological lesions.