Distribution of HPV genotypes among women with abnormal cytology results in Alberta, Canada

Abstract

Background: Persistent infection with a subset of human papillomavirus (HPV) genotypes can cause abnormal cytology and invasive cervical cancer. This study examines the circulating HPV genotype strains in a local population of the province of Alberta (a largely unvaccinated population) to establish baseline frequency of vaccine and non-vaccine genotypes causing abnormal cervical cytology. Method: Remnant liquid-based cytology specimens from the Alberta Cervical Cancer Screening Program (March 2014–January 2016) were examined. Only specimens from women who had a cytology grading of atypical squamous cells of undetermined significance or higher were included. HPV genotype was determined for all samples, and results were stratified by demographics and cytology results. Results: Forty-four unique HPV genotypes were identified from 4,794 samples. Of the 4,241 samples with a genotype identified, the most common genotypes were HPV 16, 18, 31, and 51, with 1,599 (37.7%), 441 (12.2%), 329 (7.8%), and 354 (8.4%), respectively. HPV9 vaccine genotypes made up 73.2% of these genotyped samples. Compared with specimens in which HPV9 vaccine genotypes were not detected, those with a genotype covered by the HPV9 vaccine were from younger women (33 y [interquartile range {IQR] 28 to 42] versus 40 y [IQR 32 to 51]; p < 0.00001). Conclusions: The baseline distribution of HPV genotypes in this largely unvaccinated population indicates that the HPV 9 vaccine provides good protection from high-risk HPV infections. Determining the frequency of genotypes causing abnormal cytology in this population post–vaccine implementation will be important to assess efficacy of vaccination and monitor for any potential genotype replacement.