Accuracy and Reproducibility of Cytology Triage in a HPV-Based Primary Screening Setting: A Revision of 384 Pap Tests

Abstract

Introduction: After the transition toward the HPV-based screening protocol, which has led to an increase in sensitivity, and in order to bring the specificity back to acceptable values, cytology underwent a change of approach, becoming a triage test. For these reasons, in the Tuscany region (after the recommendations of the GISCi document), it was decided to reduce, as much as possible, the use of ASC-US category in cytology triage, classifying these morphological cases as negative for intraepithelial lesion or malignancies (NILM) or LSIL, basing on the grade of nuclear atypia. So, in Italy, in a cytology triage context (HPV primary screening), a modified Bethesda system (TBS) is currently used. The aim of this study was to evaluate the performance of the review activity of 384 cytology triage cases and of the cervical cancer screening indicators (sensitivity and specificity for CIN2+ lesions) using the TBS 2014 or the modified TBS.

Materials and methods: 384 HPV positive cases at one-year recall (192 with a cytology result of NILM both at baseline and at one-year recall; 192 with a cytology result of NILM at baseline but abnormal at one-year recall), all with a histologically confirmed result (128 CIN2+, 256 ≤ CIN1), were selected, and their baseline Pap tests were reviewed in blind mode by 5 expert cytologists.

Results: The cytological results of NILM were confirmed for 92.5% and 83.8% of cases using TBS 2014 or modified TBS, respectively. 20/128 CIN2+ cases could have been reported at the baseline cytology triage, causing an anticipatory effect and an improvement in sensitivity of the screening protocol at baseline (+15.6%). Using TBS 2014, the number of false positives more than tripled with respect to the modified TBS 2014, with a significant increase in unnecessary colposcopies (+11.4%).

Conclusion: This work demonstrated that a greater expertise of cytologists, acquired during the following 3 years of experience with cytological triage, and a strong IQC system could lead to the identification of a significant number of lesions reported to baseline rather than at one-year recall (diagnostic anticipation).

Keywords: ASC-US in cytology triage; Cytology triage; Pap test review; Peer review IQC; Reproducibility.