The Impact of Triage for Atypical Squamous Cells of Undetermined Significance with Human Papillomavirus Testing in Cervical Cancer Screening in Japan.

Background: One of the features of cervical cancer screening using the combination of cytology and human papillomavirus (HPV) testing is the triage for atypical squamous cells of undetermined significance (ASC-US). The effectiveness of the triage has been recognized widely. However, there are few reports evaluating this triage process in Japan. Material and Methods: We retrospectively examined the results of cytology and HPV co-testing for cervical cancer screening in the Oyama area of Tochigi Prefecture between 2012 and 2014. Women who were ASC-US/HPV positive and had cytologic abnormalities [low-grade squamous intraepithelial lesions (LSIL) or worse] were examined by colposcopy. The results of the colposcopy testing were evaluated. In addition, we also examined the results of those who underwent co-testing a year after a ASC-US/HPV-negative result. Results: A total of 21,342 women received their first screening test during the study period, with 542 (2.5%) found to have ASC-US. Of the ASC-US-positive women, 289 (53.3%) were also HPV positive. The prevalence of CIN+ (cervical intraepithelial neoplasia or higher) in the ASC-US/HPV-positive group was 63.2%, with 81.8%, 16.4% and 4.8%. showing CIN 1, CIN 2 and CIN 3+, respectively. The prevalence of CIN+ in the LSIL group was 66.8%, with the majority having a low risk CIN 1 (76.6%) compared to CIN 2 (18.6%), and CIN 3+ (4.8%). No significant difference was observed between the LSIL and ASC-US/ HPV-positive groups. The prevalence of women diagnosed with CIN in the ASC-US/HPV-negative group, following co-testing a year after colposcopy was low (3%). Conclusions: The ASC-US/HPV-positive group was comparable to the LSIL group in terms of prevalence of CIN+ lesions. Furthermore, low CIN prevalence after one year in the ASCUS/ HPV-negative group provides confirmation that the screening interval could be extended. The application of HPV triage (which is routine in other countries) to identify these groups would be of benefit in Japan.