Prevalence of non 16/18 high risk human papilloma virus as a quality metric in gynecological cytology

Human papillomavirus (HPV) is the most common sexually transmitted pathogen that causes anogenital disease. Cervical screening by cytology and HPV testing (co-testing) are important in prevention of cervical cancer. The Bethesda System category of atypical squamous cells (ASC) is used when a neoplastic process cannot be confidently identified. In such cases, the differential diagnosis is broad and includes benign conditions. Monitoring of ASC/SIL ratio is a commonly used laboratory quality assurance measure to prevent over- or under-use of this category. High risk human papillomavirus (hr-HPV) has been used in conjunction with the ASC/SIL ratio in determining whether a particular pathologist is over/under-using the indefinite category. However, the laboratory overall sample population prevalence rate of hr-HPV subtypes has not been previously examined for association with the ASC rate. In this study, the relationships between ASC/SIL ratio and hr-HPV prevalence rate and hr-HPV subtypes (16/18 and non-16/18) to the laboratory ASC prevalence were studied. The results demonstrate that HPV non-16/18 is the main subtype which is associated with ASC-US category. A large proportion of non-16/18 HPV-related cases are seen in young patients, which largely abates by the by fourth decade. In addition, there are differences in the ASC/SIL ratio for HPV 16/18 and non-16/18 types. The overall ASC/SIL ratio is an average of the ASC/SIL rate for the non-16/18 population and the HPV 16/18 population. Instead of basing the laboratory and practitioners' quality indicator solely on ASC/SIL ratio, the overall prevalence of HPV and its subtype ratio should also be reported as they are more reflective of laboratory performance.